Another option is to sell a bunch of your stuff or pawn it. Ipod, PSP, Xbox360, game etc..anything nice you have sell it to get some cash. Also, cut back on shit especially smoking, no eating out, dating; you need every dime you can save. Get credit card cash advance, pony up the money and set another meeting. You should be able to get a couple thousand. If this isn't enough for them, tell him straight up this is what you have and set up a payment plan. They are businessmen and know they won't get paid if they put you in the hospital.
Everyone is telling you what to do but aren't in your shoes and you're only 18, you are young and don't have the life experiences that many on here have. I suggest you take our advice, work your ass off to pay them back, go to GA, and move on in life. Your problems compared to others are small. People are losing their house, wife/family, jobs, etc..their problems are way bigger than yours. You just have to pay back money which shouldn't be too hard over a year considering you live with your parents with no other expenses.
Years down the line, you will hopefully look back on this and realize how hard you had to work to pay this off and never lay another bet again. Take the easy way out and you'll be in the same spot within a year except with a bigger debt. Good luck!