I think you have to do the power plant thing first. Just go to the power plant (it's right next to Cerulean) and talk to the people there, then you'll know what to do. You can't even wake up the snorlax without doing this anyway.
ummm i thought u had to goto lavender town to wake up snorelax. u talk to the guy in radio station and then goto snorlax. open pokegear and move curser to very top and it plays pokeflute music. talk to snorelax and he wakes up. then the battle starts and you can either catch him or kill him. hope i helped!