I enlisted as an interrogator and linguist after college. To the OP, of course there are times when you regret the decision, but like anything else, you own up to it, and you move on with your situation. I vividly remember getting off the bus in Basic, with maybe 100 lbs. of equipment in 2 duffle bags and a rucksack, and being screamed at to run around the barracks twice, and then dump all my gear into one sidewalk square for inventory. If anyone did something the drill sergeants didn't like, everyone did push ups, sit ups, etc. By the end of that few hours, there wasn't one muscle fiber that hadn't been maxed out. I'd say about that moment, I regretted the decision, but what are you going to do?
To the Q? post, the specific language you obtain will be based on your ASVAB and DLAB tests. The higher the scores, the more difficult the language. I'm sure you can look those up online for info. I found after the fact from a recruiter I served with that the language identifier in your MOS is assigned on your initial orders, so the contract, in its own way, designates your language. I was a 97EPAD . . . Basically, 97E is MOS designator for Interrogator, P is designator for paratrooper, AD is designator for Arabic. The recruiters don't explain that, and may not really even know what it means to be "AD," as many of them are grunts, etc., but they can look it up, or you can take that assigned MOS code they are offering and figure it out before you sign anything. And, like buying a car, be prepared to walk until you get what you want. You are dealing with the military's version of salesman, mutt and jeff, good cop / bad cop, however they pull it off, they will pressure you to execute the contract. You just have to be specific, withstand the pressure, and demand what you want on the contract.