Might not rain, you may have a lovely sunny week, you may have a few daus of bad weather.
It depends what type of birds you want to see.....ducks and waders are probably not bothered about rain, whilst non-waterbirds will take to shelter often in silence. But birding just after heavy rain can be excellent. Birding is obviously pleasant in nice conditions, but in the middle of every hot day, and in the afternoon, it can appear quiet. Birds are not too different to us, they like an afternoon siesta! Best activity is often morning, then early evening can also be good.
I woul spend the best part of a day at S'Albufera, from about 8am onwards if possible abd certainly not starting later than 9am. Having said that, this excellent reserve with hides is good at any time. Choose nice clear days to go to Formenta peninsula, Cuber Reservoir (for vultures), and Boquer valley. Again, I would start off as early as possible.