Good places to stay in Spain Watch
But seriously maybe Barcelona - expensive but I have lots of recommendations from Spanish people and it'll definitely have nightlife. Be ready for Spanish nightlife though - start drinking at about 11, arrive at the club at about 2, party until 7/8 or so...
3 of us are going on a girl's holiday in July, we're 18. Looking for somewhere where other young people will go but not trashy and too wild however with plenty of nightlife. Preferably somewhere also good beaches, scenic and stuff to do during the day. We're considering Marbella/puerto banus and wondering if anyone has any other suggestions or views on those places? Cheers!
Spain is a great choice for your combination of beaches/culture and nightlife.
When I travel to beach towns, I find that in the height of summer beaches can be very crowded when they're one of the main tourist attractions of a big seaside city.
One idea could be to go to big city for your culture and nightlife, and then take a day trip if the kind of beach experience you're looking for isn't met where you are. You can take cheap day trips from Barcelona that will be around 10 euros return on the train.
If you have any questions, let me know!