The utilities go off ocasionally yes, but they rectify it pretty much right away if you ring. If you explain this to your guests they should be understanding. As for the tenants renting in the summer, you might want to give them the option as they may well complain if not made aware of it before renting.
We wont be able to be confident of it not happening until we are on utility contracts badger, and there is no sign of that happening any time soon. Its inconvenient but quite livable if you know it may happen and have the numbers to ring for assistance.
Juan antonio is still with the company as far as i am aware and deals with Arenal duquesa and Arenal golf. He is no longer based on site permanently but there is always somebody. At the moment it is Alfonso. Pdrich posted some numbers earlier