learning spanish

Hard to say; it depends on you. Some people find it much easier than others to master a foreign language.

Instead of going to a university for Spanish instruction, I recommend you consider a program like that of Instituto Intercultural del Caribe http://www.edase.com/english/home.htm

There are branches in Sosua and Santo Domingo. All they teach is Spanish and their courses are immersion type.

Interesting idea. Responding to your question, I would say that one year would be a bare minimum. If you are not too old, have an aptitude for foreign language (think did you do well in English grammar or do you know another language?), and if you have a very good Spanish teacher/school I personally think it is entirely possible. Don't expect to be "fluent" in one year. You could however, have a thorough understanding of basic grammar/ sentence structure etc. In short, you could, with the right opportunities and abilities, have a complete foundation on which to later build vocabulary and fluidity. Remember, there are foreigners who have been here for 5, 10, even 20 years and more who would find it impossible or have great difficulty studying in a Spanish university.

While I don't live in the DR, I have some experience at attending university classes taught in Spanish. It can be tough without a lot of preparation. I understood what was being said, but I didn't always get the proper understandings and nuances. It took the support and help from the other students after class to really get the idea.

If I remember from your previous posts, you are going to spend a few years in the merchant marines. There are several ways that you can use this time to prepare without a lot of expense. When you finally get to the university in DR, hopefully you will get the full benefit from the classes funded by the GI benefits.

There are some very good basic courses out there. When I went through Gylnco, we were taught using a course based on the Foreign Service Institute methods. They are available at places like Barnes and Noble for a reasonable price.(USD 80-90) Another agency I worked for, taught using the Pimsleur method. The comprehensive Pimsleur courses are kind of expensive, but they very much worth it, and they are discounted all over the web.(USD 180 +)

Both methods are great for learning on the ship.

The best part of learning while at sea is that the crews are filled with many native speakers to practice with. In my experience, almost all the utility positions on ship were filled with people from places like Puerto Rico.(US flagged ship) You will always find someone willing to help if for no other reason than it helps to pass the time at sea.

These steps won't make you fluent, but you will have a big step up when you land in the DR and start learning the language from one of the courses others are mentioning.

I have a good friend in Sosua who works as a chief engineer on the ships. He is approximately 3 months at sea and 3 months at home with his family. When the time comes to report, the company flies him to whatever country the ship is in at the time. Seems to work out well for him, and such an arrangement might be good for you. During your periods off you could immerse yourself in language instruction, then perhaps practice with crew members who speak that language on the ship.