How Does College/University system in Cali Colombia work

You're going to have to do planning and research on US universities, too.  I suggest you research some US universities where he might go as a post-graduate and see what university degrees/programs they honor and accept from universities in Cali and other Colombian cities.  Not all of them are going to be accepted by US universities.

The Universidad del Valle in the southern part of Cali is a pretty good university:
http://www.univalle.edu.co/      in Spanish, and
http://www.univalle.edu.co/english/index.html      in English.

Perhaps his aunt in Cali can do some research and find out costs.

I would suggest she contact via phone or email, the address listed next to 'Costos de matrícula' here for AREA DE MATRICULA FINANCIERA:

http://www.univalle.edu.co/comentarios/

According to what I have been told one needs to be in Colombia to get all of this information
First there are subscriptions for testing to see if one qualifies to go to university in Colombia
One must have a valid cedula which is best to apply for in Colombia.  The reason is that the cedula numbers given overseas from the consulates identify you as a person living outside of Colombia and you will have a hard time proving your strata to qualify for a reduced fee (if you qualify for it).
Your strata level depends on where you live.  Which means that you will have to bring proof of the location where you live or your parents live and the high school you graduated from.  If you live in an expensive area of town you will have to pay what the strata level says. As far as I know there are no student loans in Colombia.  There are just loans and they are expensive.
I believe that a semester in Colombia in a public university can cost as low as 80 or 90 dollars but one has to have proof where on comes from so if one graduated from a high school in the USA there is a good chance one will be paying the highest fee on the sliding fee scale.  Also it is very difficult for a person who graduates from a high school in USA to pass the admissions test of a university public or private. An admissions test is also given to attend any high school and the tests are very difficult to pass. A young person going to Colombia to be admitted to any high school would almost always be placed a couple of years behind. If you go to Colombia to attend an American or British school you will automatically be placed at the highest strata. If I find better updated info I will make sure to update it.
Almost forgot to mention that the competition to get admitted to university in Colombia is arduous and that I have known people (many young people) who apply for years (6 or more years) before they are admitted.  One has to present a test for every degree one is contemplating in hopes one is admitted in one of them.
Another problem is that The United States does not accept degrees from universities in Colombia.  If one wants to transfer to the states one has to do the schooling all over again. So doctors with experience in any field have to go to the USA and no matter the experience they have to start all over again.

I would encourage this person to tackle his or her education in the states, apply for the educational loans available , stay in state and enjoy the wonderful freedoms we have in the USA. By the way a degree gotten in the USA is accepted almost all over the world.  If this person does not have money to pay for school I strongly encourage him or her to serve in the military.  A small price to pay for the opportunities that are offered. One can have a very successful life in the military and one can develop an amazing self value by impressing oneself with discipline and dedication. if he or she loves it one can stay 20 years and retire still young enough to have a second life. If he or she attends two years of junior college he or she can enter as an officer and get paid a better salary.

Here is a small update on my previous comment.
http://www.icfes.gov.co/
At this link you can find the information related to the test that needs to be taken to qualify for university.  Your student might have to "validar el bachillerato" or get a GED to qualify for university if your student graduated from a high school in the states.

. The young man that I am helping who wants to go to college is not legal to go to school or live in the USA. HE is a Colombian citizen so the US military is not an option. He is 30 years old so he has not been to HS for a long time. Pre testing to get into University in Colombia might be tough for him. I am going to ask him to check and see if there are any classes that tutor for the college tests. In the US, they have courses you can take to help you with your SAT's.