San Juan Del Sur has zero surf and lots of fast food restaurants, kindof a bad joke, cute downtown with lots of places to stay and great restaurants but expensive and nothing to do there. There is a good surf break 20 minute drive from SJDS at Playa Maderas. There are a couple of different places to stay at maderas, but not many.
Popoyo is a cool little town with epic surf and it's dirt cheap. Terrible food and it's an advanced break but definitely the place if you're into surf.
Tip 1 - Ride public transport instead of renting a car, it's cheap and easy and my good friends were almost killed by bandits while driving a rental car at night.
Tip 2 - If you go anywhere near Managua, there is a super nice volcano lake to stay at just 30 minutes away. Very peaceful and great spot if you get in late or the night before flying out. We had an early flight out and stayed there the night before and it was easy to take a taxi in the morning.