You should be able to pick up the MOS you choose with a score as such. I'm telling you man, you are going to be kicking yourself in the rear by choosing infantry. All Marines are rifleman, and you will get your time in "the shit," just remember these three things:
1) Infantry gets treated like shit by everyone including their own.
2) Promotion in infantry is virtually impossible.
3) When you get out, your job options will be limited to only a cop, however cops take in non-felons too, so you can see your competition.
Pick a job that will allow you to be in the shit but also have advancement opportunities such as anything in communications (fast promotions and is stationed in infantry/ grunt battalions) or logistics (this job will be important after you get out)
In my company, even the computer guys were in the shit. How do you think all of those special gismos are hooked up in Iraq and Afghanistan, because of those guys.
Furthermore, by performing well in any job in the Marines, you will be eligible for Recon/ Sniper School, and you could even get to those special duties even as an administrative guy.
I remember, I was just like you. I didn't care what I was going to do, all I new is that I wanted to be a Marine. I went in open and got put into communications. I performed well and went on a special duty, which i was able to meet the president, collin powell, and rice. Less than a year later I got out and the only job I could get, besides becoming a cop, was cleaning toilets (house keeping) in a hospital.
BE SMART BRO, and do a job that is beneficial in the future. Your poor decisions now will get catch up to you in the future so make smart choices now and work towards the life you want after you get out.
Theo...your advice is rite "on point".