Seville during April Fair

I don't know whether schedules change during the Fair; my only recent trip to Seville was during Holy Week, and there were definitely significant changes then, but that was often because large processions were blocking passage to the tourist attraction or church. Some of the tourist offices in Andalucia had a one-page handout summarizing opening hours for most of the local sights. I don't remember seeing that for Seville, but I probably didn't ask for it. I later found one or two of them posted online, so with some diligence you might be able get the information before you leave home. However, I doubt that it would be available very early.

I think you'll probably need to hit the individual websites to check for exceptional hours, if any, if you don't want to wait until you arrive in town to ask the tourist office folks.