Well, its mostly about velocity and to a lesser extent playing in a competitive league if the velocity is so so. It also doesn't hurt to get into a good college summer league and have good results with so so velocity.
For the most part you are looking at just about any league in SoCal and the Big 8 in NorCal. Yes you can find success at a school not in those leagues, however, these are the leagues that are scouted the most.
The larger the JC, the better chance you have to get the classes you need to transfer....as long at the AD gets priorty signups for its players.
This is all pretty good information. My son is a LHP at a NorCal JC. I don't know how true the part is about looking at any league in SoCal...it seems there are a couple conferences that aren't very competitive, but definitely Big 8 in NorCal and OE in SoCal would probably be the top two conferences.
And because of priority, obtaining classes has never been a problem.
KANDKFUNK, don't know much about PNW JCs, but PM me if you have any specific questions about CA JCs.