"They are trying Mexican food."
Translation:Ellos prueban comida mexicana.
I agree that "están probando" should also be accepted, but with the understanding that native Spanish speakers use the present continuous tense more rarely than English speakers use the corresponding English tense.
What else I would like to know is why "la comida mexicana" isn't used instead of just "comida mexicana."
The kind of food is specified by the English adjective "Mexican." The word "comida" is a Spanish noun, and hence, a "Mexican" word. However, this doesn't mean that the FOOD itself is Mexican. In other words, the Spanish word "comida" means "food" in general rather than a specific type of food. To indicate a specific food, you must use an adjective in both Spanish and English, for example, Prueban la comida china/They try Chinese food.