Maaaan...for one thing, the food is amazing and the women are some of the finest you'll ever see. We took an excursion to these two private islands and it was incredible. The city is surrounded by a giant wall - they call it the Old City - and the entrances to the city are protected by federal troops with uzis.
Once you go outside the Old City walls you're in the city proper, and it's rather lively. You can't come down here flossin'...not only will you potentially get got, but more particularly, you make yourself a target for beggars and merchants and these folks are EXTEMELY aggressive. Last night these girls were fighting over me and my wife's attention for who they could get to buy diapers for their babies (they were camped out in front of this drug store we went to, getting some bottled water).
The money situation is cool, they don't really take American cash but they do take credit cards (check with your bank or provider first, though, to see if they'll try to crack you for international rates). It's probably best to just exchange it anyway, the Colombian peso is not as valuable as the dollar ($100 is roughly 400,000 pesos). Also, Uber is vibrant here and super cheap. Make sure you take IT, and not a taxi. They'll try to get you for the "gringo tax" if you do. We've taken nothing but Uber and its been straight.
Another thing is...dawg its hot as SHYT down here. Real extra humid hot. So make sure that wherever you stay has air and be prepared to dress accordingly.
Recomended spots:
Ana's Dinner Experience (food and drinks were unbelievable and the dinner show runs about every 15 minutes, with THE FINEST female dancers you'll ever see)
Good Ely - outside the Old City walls, take an Uber there. Breakfast was amazing.
Apogeo Restaurante - rooftop restaurant and bar where you share food plates. Food was stupendous and the drinks were unique.
Overall, I highly recommend it. Also, we had to stay overnight in Panama City before we flew here, and THAT place is even MORE amazing this this one! Highly recommend that, too.