Canonically, we don't know because we don't know of any romantic relationships Jango had with either men or women.
The fact that Jango did not have a child with a woman does not really indicate he's homosexual -- he is willing to have a son
but perhaps he never found a suitable woman to be the mother.
In Legends, he is heterosexual.
He has a romantic relationship with a woman named Sheeka Tull .
Legends also provides the backstory for Jango's recruitment as clone template.
The ending to the video game Star Wars
Bounty Hunter includes a scene in which Darth Tyranus first recruits Jango.
Tyranus sells the idea to Jango as a chance for "immortality", and to pass on his ways to the clone army.
This convinced Jango to become the clone template for the army and possibly for Boba (he could pass on his ways to Boba in particular), but when Tyranus asks him why he wanted an unaltered clone Jango refuses to answer.
So even Legends only hints at why Jango wanted a son.
scifi.stackexchange.com/users/31936/Null
Because he wanted an exact replica of himself.
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I don't think Jango Fett actively sought to have a son via cloning.
Rather, thinks happened the other way around.
The Republic approached him and bought his DNA to produce a clone army.
In return, Fett decided that, if they were going to clone him, he wanted one to raise as his own.
In other words, the opportunity to have a son presented itself through the clone process, so he took advantage of it.
If he truly wanted a son, it wouldn't have mattered if he was homosexual or not.
There are plenty of options for "natural born" children other than heterosexual sex, including adoption or artificial insemination.
(Having said that, there's no indication that he's homosexual, and as @Null points out, at least one non-canon case of his having a heterosexual relationship.
Again, that's not proof -- homosexual men in the real world do sometimes "fake it" for various reasons.
It merely shows that we just don't know enough about him to know.)
scifi.stackexchange.com/users/2816/KutuluMike
A woman?
Dating?
Ain't nobody got time fo' dat!
Seriously, he's the galaxy's most notorious bounty hunter and (according to Legends canon)
one of the last living true Mandalorians.
He also wants something very specific - not just a child, but a son that he can raise in his own image.
Doing things the "old-fashioned way" would require: Finding a potential mate, one who would be genetically compatible with Fett's standards Establishing a relationship with that mate Impregnating the mate with viable offspring A 50/50 chance that the offspring would be male
An even lower chance that the offspring would have the right genetic makeup for what Fett intended A healthy birth with no complications Dealing with the mother
(provided Jango did not want her involved in the raising of the offspring, which is likely unless she was a Mandalorian warrior) Long story short
, Jango Fett is an extremely practical man.
And when a practical, yet efficient method of getting what you want is presented to you, you take it.
It's entirely possible
that, had Dooku's offer never come along, Fett would have eventually attempted to settle down and have a son the old-fashioned way.
As it stands, however, he was presented with an excellent opportunity to get a son without any of the added steps or "baggage" he would have to deal with otherwise.
scifi.stackexchange.com/users/20557/Omegacron
Based only on my take from watching the movies, I imagine Fett as a sort of elitist, perhaps even a eugenics advocate, that believes that there is no further improvement to be made to his genes and that the best way to continue his blood line is by simple replication.
This doesn't have to be expressed in specific physical or mental characteristics and could just be a matter of ego.
If I was to develop this story further, here are some cute ideas: He has a secret that must be passed on which he will trust no one with but himself.
Some information was encoded in his DNA which will be lost if it is modified.
There is somewhere something of importance such as a treasure or an heirloom which can only be accessed with his DNA but may be fatal so he wants someone else to take the fall.
He wants to extend his life by transferring his consciousness to the boy when he comes of age.
As I was writing, the last option actually rings well with Tyranus's promise of immortality and the fact that we know that force users can still maintain a degree of control after they have died and returned to the force, If Fett knew this then he may have been looking for a body to return to.
He might also have some or all of the knowledge of Darth Plagueis which would connect a lot of points in the story.
scifi.stackexchange.com/users/42844/Tamir Daniely
Why did Jango Fett choose to have his son, Boba Fett, created via cloning, rather than having a child by a woman?   Did he want a son and was either unwilling or unable to do so with a mate?
Why did Jango Fett have a son via cloning instead of through natural reproductive processes?
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scifi.stackexchange.com/questions/83490
scifi.stackexchange.com/users/20502/Rodrigo Gurgel
Tyranus sells the idea to Jango as a chance for "immortality", and to pass on his ways to the clone army. Some information is encoded in his DNA which will be lost if it is modified.  There may also be something important that can only be accessed with his DNA or he may also want to extend his life by transferring his consciousness to the boy at a later date. There is little information available on Jango’s relationships, but he was likely drawn to cloning because of the concepts of immortality and replication. Moreover, Fett may believe his genes are perfect and that his DNA bears a treasure he wants his offspring to access without his DNA being modified. 
There is little information available on Jango’s sexual orientation and his relationships with men and women. He may not have purposefully sought to have a child via cloning but is likely drawn to the idea of immortality and replication associated with cloning. Fett may be an elitist who believes his genes are perfect and that his DNA contains a treasure or an heirloom that he wants someone else to access without his DNA being modified. 