Here are some ideas.
Sea to Sky corridor. Brohm Lake, Alice Lake, Browning Lake in Squamish offer some trout fishing and shore access is plentiful. Brohm Lake is just north of Squamish, it's a small lake and access is just off the highway. It will be stocked at least once before early May with rainbow trout (12 inches, 250 grams) that anglers can keep. The lake also has an abundant population of cutthroat trout, but they are generally small (6 inches). Browning Lake is the little one before you arrive in Squamish. Access is again just off the highway so both Brohm and Browning can be noisy at times (Browning is noisier than Brohm since part of Brohm is a bit further away from the highway and seperated by trees). Alice Lake is no longer or rarely stocked with rainbow trout but it still has trout in it. There is a campground at Alice Lake but I am not familiar with its opening period.
A bit further north, Alta Lake in Whistler has good rainbow trout and cutthroat trout fishing at times, but shore access is limited to a pier at the park on the east side. It's a total catch and release lake and no bait is allowed. Not sure about camping in Whistler, plus it's still quite cold in May.
One last (and warmer) option, see:
http://www.fishingwithrod.com/yabbse/index.php?topic=17169.0The resort mentioned in the above thread has relatively easy shore fishing for yellow perch, bass and trout. We'll be there during the weekend of 2nd - 4th.