I think you received bad advice about carrying cash. I carry it all the time; howefer, I divide it among my pockets. If I'm going to a stip club I wear a pocket T-shirt inside out. I put my money and DL in the T-shirt pocket thus reducing my risk of a pick pocket getting my stuff. (I leave my wallet at home or in my car and only carry what I need.)
I suggest you carry a lot of ones and fives. Nobody in TJ can make change. If you hand a waiter a $20.00 he'll porbably go home and you'll never get your change.
Be careful using an ATM. A lot of bad guys stake them out. Clubs and bars don't have ATMs, so you need cash to enter with cash. Also, almost all ATMs dispense pesos. So you pay the exchange rate twice if you return to the US with pesos.
Bars don't take credit cards either. In general avoid using credit cards in TJ except when necessary in upscale hotels and restaurants. Clerks and waiters tend to record and sell credit card numbers.
May I suggest you read the Newbie Guide to Tijuana in the FAQ forum of www dot tjamigos dot com. I think it--and the other infromation there--will answer a lot of your questions and help make your trip safer and more enjoyable.