the Saiyans soon had an alliance with the Humans and the Namekians. Despite seeing themselves as a different species, they are really just a step away from being humans with the new biology.
The 'Capitol' of the Saiyans is just a giant town based around the former 'Capsule corp' Headquarters.
There are two famous Saiyan families, the Vegeta's are famous for being the strongest, and the Son's for being the 'weakest' for not being ruthless.