Barona seems to like to manage their tables to fullness. It's annoying. And finding good DD penetration in San Diego is tough in general.
Where crowded tables (especially DD, especially poorly penetrated) really hurt you is if you're employing any sort of cover (limiting the amount you increase or decrease your bets). Because the count is going to jump a lot each round due to all the cards being used, and worse yet, you're not going to get in that many rounds.
http://www.blackjackincolor.com/cardcountingcover3.htm
However, if you're not worried about cover, then playing at a full table isn't so bad, as long as you can put up with the crushing boredom.
edit: oh yeah, I tried simming Barona's game, and I got less optimistic results regarding win rate than you did. Maybe half as big if you're talking $25-$150.