What kind of stuff should I be doing to get myself to be jam ready besides learning scales and learning to identify pitches by ear?
Also, at what point in playing bass did you feel comfortable with the idea of playing alongside others?
Your guitar friends are more than happy if you're able to pound out root notes in a halfway steady pattern.
When I was 14, I joined a band, then bought a bass. I came home with the bass and had the first rehearsal on the evening of that day. The guitarists showed me which side is up and how to fret a note.
I played happily with the others (who were also quite happy) until I started dripping blood on the carpet (actually quite a bit longer - until the carpet owner noticed).
I started with lessons a while later.