I have not been there in May, but would guess that it is not crowded. Schools are not out yet, so I would think it would be kind of like it is in late October/early November. (We have been then and it was not crowded at all.)
As retirees, we tend to choose times when the resorts are less crowded. We do go to PV every November and Thanksgiving week is generally busy, but the week before and week after are not. So we make a point to be there during the slower time too. We like being there when it is not so crowded at the restaurants, beaches, and town.
When we were not retired and lived in the mid-west, we always went in February with all the other folks escaping snow! It was always crowded and we had to get up early to get spots near the pool or beach.