I took four years of Spanish in high school. Senor Monahan only allowed us to speak Spanish in class. Nothing was spoken in English. We had three weeks of instruction of the Italian language and the French language during our Junior and Senior years. He taught us in Spanish.
The purpose was twofold. The first was to show us how much Spanish we did know. The second was to show us the similarities among the languages for comparison.
If you do wish you had taken Spanish, you might speak with a knowledgeable Spanish instructor and see if there are recommendations in taking classes and a time-line in achievement, depending on the level of proficiency you wish to gain. This is not to say that you abandon your present thoughts. If there is a university you wish to attend in France, perhaps you can immerse yourself in the Spanish language over some weekends spent in that country. Of course, that takes some money.
Just a few thoughts from this crabby person.