Potty training & Pull Ups...any success stories?

My son is 2 & a half and is fighting with me constantly because he doesn't want to wear diapers. He doesn't really have the concept of what it feels like before he pees down, so he keeps wetting his underpants. I've tried Pull Ups and he isn't phased by the "cold sensation" they're supposed to give off. I'm not really freaking out because he HAS to be potty trained at this age or anything (I'm not a textbook mommy) but I'd like to start converting because he doesn't like diapers. He has been in swimming lessons since he was 4 months old and I think he may just be used to the wetness of a bathing suit. He's not really showing any other signs of readiness except that he knows to put the potty seat on the toilet seat, jump up there & sit for a while, pull his underpants up and flush. Now to get him to do something on the potty! Thanks in advance for all your input!