It is surprising the number of people moving to Spain who expect the Spanish to speak English. Most don't. If you are living in the coastal regions, where there are many tourists, there is a good chance that they will, or at least they will have a go, quite often because their livelihood relies on it. But that doesn't alter the fact that you will be living in Spain and you should attempt to learn Spanish, if only for your own benefit. You will need to speak some Spanish, if only a basic smattering, when you visit doctors, hospital, banks, solicitors, etc., unless you prefer to employ the services of an interpreter. All local, legal and documents from electricity and telephone companies, etc., will be in Spanish, although you may find a few companies, such as insurance companies which cater for ex-pats, which provide polices in English.
Most towns and cities where a reasonable number of foreigners have settled, offer courses in Spanish. Sometimes these are organised by the local council, a local business or even private individuals. Often the local council courses are free of charge, while others make a small charge. Check your local papers for what is available.
Another method of learning Spanish is via the Internet. There are many sites offering on-line courses or selling programs that teach you at your own speed. Computer software is another way of learning Spanish.
Speaking Spanish and understanding the printed word is one thing, but understanding a Spanish speaker is another, especially if he or she is on the telephone where you see no facial expressions or hand movements. Most courses simply teach you to speak a few words in Spanish, but in reality, learning any language is made up of 4 parts - speaking, listening, reading and writing, and you will need all of those. If you live in an area where there is a strong accent this can at times be daunting. Like with most countries, there is a huge selection of accents and dialects in Spain, plus the fact that there are 4 recognised languages on the mainland, with others on the islands. Most are akin to Spanish with probably the exception of Basque, spoken in the far north, which is very different.
If you are intending to work in Spain, Spanish is usually a necessity.