Hey!
I purchased a Fender Jazz bass (Mexican version) very recently and I'm wondering if this is OK to use in a Sonic Youth / Velvets style rock n roll band. I was torn between this one and the Fender P-bass - but went for the J as it looked better (price was the same).

Any Fender users out there who can help? I can still return this to the shop and swap for a Fender P is that's more "rock n roll"

A Fender's a Fender. If you feel good playing it, stuff 'rock'n'roll'. Too many people out there(not on Talkbass, of course!) only care what a Bass looks like. Play what you want to, as long as it feels comfortable, and sod'em all.