I'd kill to be in San Diego. If people on this website actually played paintball, I'd tell you to go play some ****ing paintball in one of the best places for it, but alas, no one here plays paintball anymore.
how old are you? if you're 18 there is a cool hookah bar on garnet avenue in pacific beach off the 5 freeway. its called sinbad's. the garnet strip is a fun place to be on a friday/saturday night but if you arent 21 dont be drinking cuz cops abound.
downtown theres another hookah bar called fumari in the gaslamp district.
other then that, there are the beaches, each with their own little distinct flavor, surfing, bodyboarding, you can go hiking and stuff up in julian, but its really hot so youd probably not wanna do that.