What time of year are you asking about? Christmas and Easter book up very quickly, so you must book 11 months in advance. Most other times of the year are much easier. You could book now for summer, for example, and find a studio if you are somewhat flexible on dates. You could even book at the last minute if you aren't picky about which resort you are staying at, although I wouldn't suggest that approach if it's your only vacation this year. I have even called on Wednesday for the following Sunday, although that's just a last-minute get-away.