everywhere just opens up for summer. if you are here for the last weekend of april/start of may there will be a good amount of parties (defected festival, pacha opening, pyramid at amnesia, IMS, dc10 etc). that should attract a good number of people, but the island will be far from full.
weather wise you can get anything from 25ºc daytime and sun, but you also might get a rainy day or two (and sometimes wind).
lastly, even if it's sunny, in the evenings it'll still be cool so bring a jumper or a light jacket!