Where you should invest in the US depends on your goals and strategies. As you mentioned, CA has proven to be a good place for appreciation over the years, but is in a depressed state and will remain that way for at least another 18 months. If you were to invest in CA, expect the value to drop more, creating a longer span before you can sell for a profit. In addition, investing in CA would be a speculation play, not a cash flow one. Even if you can buy at 50% of value, you would be lucky to just cover your expenses.
On the other hand, as Cummins stated, Texas is a completely different environment. Houston and even more so, the Dallas/Fort Worth Metroplex, have undervalued RE, job growth, and population growth. You can also buy with a very small cash investment and cash flow the property. While you most likely will never see 20% + appreciation rates in Texas, you also will not see that kind of drop either.
It all comes down to your investment style - cash flow (+long term future appreciation) or speculation which ultimately will require you to carry a negative cash flow until the time of sell/market recovery.
As far as Realtors go, finding an experienced and competent one will be a task. Make sure they deal with investors on a regular basis, make sure they invest themselves (practice what they preach), and always get multiple professional opinions on the advice they give you.