don't go the ESL route bro, that's just a waste of time and money. i don't know about the institutes that offer TOEFL classes but what I can say is those classes are not necessary. I didn't go to any institute, I studied on my own and saved time and money. 
I studied for about a month at home, took the practice tests given in the book (the book i used was Barron's) and went to take the test (it was IBT). I got a fairly good score for just a month's self-study (101 out of 120). I did worst in my speaking section (21/30) because I didn't practice well, and writing was okay (24/30) but i did really well in the other two sections - reading and listening (28/30 each).
You've been in the states for 4 years which means you know english pretty good, you can do really well. Be confident, it's not that hard. If you study well for 2 months, you'll rock! But give some more time to prepare for writing and speaking section because we Nepali tend to be lazy in writing and hesitant in speaking.
Go for it, you'll do just fine, you just have to be confident and everything will turn out right.