The most popular with English speakers in Europe is the Camping Cuidad Zarazoga. This is highly rated because it has all the facilities you could want such as swimming pool and on-site entertainment, and is also very well situated within walking distance of bars, restaurants etc.

However, this is the best campsite from a family holiday point of view, which may not be your point of view. If you want more detailed information, you could try a trusted campsite reviewer such as Alan Rogers. They have inspected over 500 campsites in Spain, and the good thing is that you can look on the right of the page to narrow the search to find the best place for you. For example, if you want to find a bar on site, be near the sea etc, you include these items in your search. Or you could look for 'family friendly' 'adult only' or whatever is best for your needs.