I currently work as an instructor in Florida and I have talked to many of the schools you have mentioned. The problem that you will find is trying to balance the price with the quality.
My goal was to finish quickly (4 months) and the school I went to was able to make it happen. There price is also quite reasonable. The name is Florida Aviation Academy in Pompano Beach Florida. The other schools you mentioned like Delta Connection, Regional Airline Academy, and the others are very good schools with quality education but you pay $20,000 or more than you have to. Pheonix East, American Fliers, and Kemper I have heard negative things about. ADF airways is based in Miami and is also a good school. It also has a lot of pilots that come from South and Central America to do conversions or training so it is a good place to meet people. Another school I didn't see on your list was ATP. There you do all of your training on muti-engine planes with a price that is not much higher than doing it all on single.
One thing you should think about though, is that the schools that offer fast paced programs are just that, fast paced. There is a lot of pressure to finish on time and quickly. There will be a lot of information to study and learn but if your goal is the airlines then that will be like the training you will do there. I definitely agree with Panama Jack go and talk to the schools and see the operation, and also talk to the students that you will see. They will convey their concerns or praise for the school. Finally, since you are Guatemalan you should start the process early to get your M-1 visa and your TSA (Transportation and Security Administration) clearance. Both are required to start training in the United States but you need to communicate with a school to get more information on that. Hope this information helps and feel free to PM me for more information.