Ask the folks in Wilsons (I think its Wilsons...) in Bishop. You could even just ask for directions on how to get to the Happys and don't bother taking a guide, you'll have a good time just walking round the boulders just climbing whatever takes your fancy.
In fact in May the Happys could be pretty hot already (they can be hot in the middle of winter), if you want to do awesome highballs in low grades then head up to the Pollen Grains. The altitude is higher so they might be a bit cooler. Better still the scenery and all around vibe is way better than the somewhat dingy Happy boulders.