This is a great question. I'm not an interpreter by trade, but I have the Chinese language skills necessary to pass the military's linguist training.
There are a lot of options for interpreters out there. The market for Spanish interpreters can be a bit more difficult since there are many native speakers in the US. That being said, there are still many options.
The best route in my opinion would be through government service. You can do that a number of different ways:
1) The military. We need linguists who are proficient in many different languages, Spanish included. If you are a military linguist you also get a bonus every month on top of the rest of your pay and benefits. Also, if you have a knack for learning languages, the military could also send you through language training for other languages (Portuguese, French, Arabic, etc). I know there is an Air National Guard linguist unit in Utah that you could check out.
2) Foreign Service. The government has embassies and consulates all over the world, including almost every country in Central and South America. You can work in one of those locations as an interpreter. In that line of work, you will work with your counterparts from foreign governments. You can also expect to move every few years from another country, back to the State Department in DC, and then back to another country, etc. It can be a very exciting life if you enjoy traveling and living abroad.
While not the State Department, you could also look at Border Patrol, ICE, FBI, or the NSA as other places that need linguists.
3) State and local governments that are in areas with large amounts of Spanish speakers will also have interpreters. I don't know as much as this kind of work, but I know it is out there.