Unless you have an objection to down, you should consider the Kelty Cosmic 40 down in either reg or long depending on your height. These will be more packable and lighter for the same warmth than an inexpensive synthetic bag and are within reach of your budget.
You do have to keep down dry for it to be effective but for Southern California where rain/dampness is not usually a problem, down will generally be a much better choice. Kelty bags are generally well made and a good value for the price. I have the now discontinued Kelty Lightyear 20 which has been more than adequate for my 3 season Sierra trips although it has slightly better spec'ed down and is heavier than the Cosmic due to the temp rating and more generous fill weight.
I suspect the ratings on these bags are a bit optimistic but that is often a matter of personal perception. Long underwear and a bag liner can extend the range but it is important to get a good sleeping pad that will provide sufficient insulation for the conditions. An R value of around 2 is a good starting point for extended summer use.