This post about picking up single girls in Managua for sex or dating will break down the scene in full for you. Nicaragua is a cheap place to visit and you can have a lot of fun here.
Overall this is a pretty safe place, at least by Central American standards, but looks rougher than it really is. This is a spot where foreign men really stand out and picking up girls is not hard at all.
One thing to note is that taxis here are very cheap during the day but at night they really try to rip you off. Check and see if Uber is a viable option by the time you arrive. Some of the best spots to meet sexy Managua girls would be the malls like Gallerias and Metro Centro Malls. They are not only good for day game but they also have lots of nightlife as well, particularly Gallerias. Getting a condo near there would be the best way to go. The closer you are to the places you frequent the easier it is to convince girls to come back with you.
If you want to meet girls for sex in Managua nightlife try Altabar Moods at Gallerias Mall and the Karaoke Bar also at the mall are two great options. There are some other spots here as well.
The most popular club in town is definitely Chaman. It is huge and crowded later in the week. You can even upgrade to VIP for one dollar, yes, you read that correctly. If you plan to focus solely on night game then stay as close to Chaman as possible. If you are going to be more well rounded be as close to Gallerias as possible.
