Managua is well away from any oceans so you will be renting a car or some sort of bus no matter what. Though what a decent distance actually is would be helpful.

Western type experience you can stay at Barcelo Montelimar which is all inclusive and to me, horrible. I went once and that was enough and was at the request of my friend.

However they might have some sort of transport available as routine.

San Juan del Sur is youngster country (though frankly the all types of drug talk sounds like they were bragging - it's actually not that common here. I am in Managua now on maybe my 60th visit since 2004 and I have seen MJ exactly once and hard drugs never).

Apart from SJDS you have the Pochomil area (Barcelo and some small others), Poneloya (if you stayed where I took a room for a day I am in the register as Bill Clinton, Washington DC), but I think there is a quite costly eco resort or two.

It might be helpful understanding cost barriers, your Spanish, and how you'd plan to get around here.