there really is no difference between Judo and BJJ. classic japanese jiu jitsu spawned Judo. but being that it was a refined SPORT, older students of Judo often reverted back to the more martial Jiu Jitsu. so when Judo was at the end of the their world tour for promoting the sport, the top Judoka settled in Brazil and taught the Gracie family "jiu jitsu." the rest is history . . .
there's a long standing feud, or discussion . . . which is better Judo or Jiu Jitsu?
well... we could argue the chicken or the egg story forever. Judo is more stand up, and explosive . . . an international Olympic sport, as was its intention by Professor Jigoro Kano. everybody likes a good takedown or monster throw. BJJ is refined mat work. a little more macho and aggressive like the Brazilians themselves. you see similarities in both sports because they are eachother. is sambo any different? not really. what about pancrase? that's an even older sport. any similarities to judo - jiu jitsu, of course. what about roman greco wrestling?
so if you've never had the opportunity to learn Judo, just think of the transition from stand up to ground work. nobody wants to go to the ground, so take your opponent there first. strike, when they clinch, throw. now that they're on their back, choke and lock.
you might want to check out Goltz Judo in Claremont. they're fairly close to you. and there's is a competition style dojo in West Covina, i have to ask my buddy for the name.