Someone asked me to describe a few certain Colombian cities and this is the advice I had to offer.
From what I have heard, Barranquilla is not worth visiting except for Carnival. The people I met who enjoyed it there knew some locals who showed them the nightlife. Otherwise, there is not much to do there.
Cartagena and the surrounding area is worth spending 3-4 days max. 1 day exploring the old city and Boca Grande (do a chiva ride if you have never done one before), 1 day doing the Playa Blanca beach trip, and 1 day the mud volcano. From what I experienced, the nightlife is full of prostitutes and really not worth it. Definitely check out Cafe Havana for an authentic Cuban bar with a great atmosphere.
Cali is probably one of the least attractive cities I have ever visited. The only reason to visit Cali is for the Salsa dancing. You can visit some really nice and authentic salsotecas. But don’t expect to meet any women while you are at one since most people go in groups and are sitting down at tables when they are not dancing. There are also regular clubs but I did not find them to be that great. Avenida Sexta is known as the place to go but even on the weekends the clubs were not very crowded. I did go to this one area off the highway where there was a few clubs that were pretty cool, though I forget the name of the area.
If you do go, you can walk around the downtown area for a while, visit the zoo, and go to the waterpark. That is pretty much it.
Bogotá is probably my favorite city in Colombia. There is so much to do and see during the day and so many great clubs and bars to visit at night. Friday evenings is a great time to walk down La septima with lots of live performers and a huge flea market.
The entire street is closed off and its just a great time. Sundays are the ciclovia where La septima is closed off and everyone bikes through the streets. There are great views if you hike or take the cable car up Monserrate.
Most people sleep in La Candelaria and my favorite hostel is called Hostel Sue http://www.hostalsue2.com/
La Candelaria is a an artsy neighborhood with lots of students around, universities, small bars, great restaurants, museums, etc. My favorite part of Bogota. I highly recommend a small club called Escobar Rosas where you will tons of students go looking for some Gringo action.
There are some other good small clubs around La Candelaria as well. Otherwise, you will want to take a cab to the Zona Rosa for a more upscale night. Walk around the area and choose what looks like the busiest place.
You will also hear about a club called Cha Cha which is located on the 40 something floor of an abandoned Hilton Hotel. Its located on 7th avenue and 33rd Street in the “Ball Room” of the old hotel, and keeps the traditional elegant decoration. Crystal Chandeliers meet Electronic music. Has amazing views of the city at night and an amazing terrace to hang out. Frequently visited by world famous DJs.
Other areas to visit in Bogota are Usaquén, Parque 93, and the bullet proof clothing store where they will fire a pistol at you if you request it http://www.miguelcaballero.com/cms/front_content.php .
I never got to go, but Andres Carne de Res is supposed to be the best restaurant and discoteca in Colombia.
There is also Catedral de Sal de Zipaquirá which is a nice day trip.