Calfornia Tax deed sales

I am new to tax deed sales but see that there are a few tax deed sales coming up in California in February. I am planning to attend the auctions in Sacramento and San Diego this weekend to have a look. Can someone tell me if this is worthwhile to bid for or should I concentrate on preforeclosure and short sales instead?

Some of the minimum bid are less than $10,000 however, when I check their estimated market value, most of them are worth at least $200,000 and above. Anyone ever attended Califormia tax deed sale and manage to walk away with bid price of $30,000 for a house worth $200,000? Is this possible or am I wasting my time. I am flying in from Ontario Canada and will have to pay hotel and airfares to attend.