First pick for RV park would be Chula Vista. Very nice full amenity park. Look at their websites monthly newsletter for possible discount coupons.
Second choice is KOA. One of the nicer KOA's I've been too.
I've driven through Tijuana recently but have not stopped in several years. Traveled down to Rosarita and Ensenada to the south. Great beaches and restaurants there. When we have gone to TJ for an afternoon we've parked on the USA side or taken the Trolley light rail which drops you off right at the border. Then walked across for shopping along Rio Tijuana Shopping district. It's a bit of a walk but fun. Can also take a taxi (agree on fare before getting in!). There are also day trip bus tours for San Diego that make it easy.
