My bass instructor plays mostly jazz, can play bass guitar, electric upright, and double bass (as well as a bunch of other instruments); he plays what the band director / leader wants him to play. And he does play bass guitar a fair bit, both a five string and a four string. However, he also says that, even if you don't intend to play a lot / any jazz, it helps to study jazz anyway; a lot of the techniques etc you learn to play jazz will stand you in good stead in many other genres. I wanted to learn some jazz anyway, so I'm currently learning how to play bass in a jazz setting. My instructor says I'm doing fairly well, and I'm quite a bit older than the OP. Mind, I've been a FAN of jazz since my college days, so I'm not new to how jazz sounds.
Fassa, I'd encourage you to go to several of the jam sessions WITHOUT an instrument, just to listen and learn. At what level of experience are the other musicians at? Do they have some time set off for people who are fairly new at jazz? What pieces do they normally play? Is it mostly improv, or are they working from jazz standards? Are there some of them willing to play along with you, while giving you some help at learning the ins and outs of the genre? If they're geared for more experienced players, maybe someone there can help you find a group that's more oriented toward those who haven't played much jazz. Actually, if there are regular scheduled jam sessions for any type of music, it's best to show up and LISTEN ONLY the first few times you go, to see what songs they usually play, how the jams are organized, etc. Beats showing up with instrument, expecting to play, only to find out you can't play whatever they're working on, etc. Makes it a lot more fun to play, if you have some idea of what you're getting yourself into!
Any way, check out those jam sessions, and hopefully you'll find a place you can fit into, and have fun. Even if you don't do much playing, just listening and watching the other musos can be both instructive and fun!