I want to know statistical data about what is the amount and
percentage of use of the principals internet browsers in Mexico?

These statistics are grabbed from mexican websites

Try the following search, it will show statistics of mexican sites and
majority of them have stats on browsers...
://www.google.com/search?hl=en&q=site%3A.mx+webalizer&meta=

Examples: 
http://www.glib.org.mx/usage/
http://www.relaq.mx/usage/

This site receives 90 000 unique hits a month:
1 369980 16.67% Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET  
2 242533 10.93% Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1) 
3 193711 8.73% Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1 
4 188308 8.48% Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1) 
5 123152 5.55% Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0) 
6 72494 3.27% Mozilla/4.0 (compatible; MSIE 6.0; Windows 98) 
7 70219 3.16% Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; .NET CLR 1 
8 59711 2.69% Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; FunWebProd 
9 45556 2.05% Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.5) Gec 
10 36330 1.64% ia_archiver 
11 32501 1.46% Mozilla/5.0 (compatible; Yahoo! Slurp; http://help.yahoo.com/ 
12 25951 1.17% Mozilla/4.0 (compatible; MSIE 6.0; Windows 98; Win 9x 4.90) 
13 23501 1.06% Mozilla/4.0 (compatible; MSIE 6.0; AOL 9.0; Windows NT 5.1; S 
14 23188 1.04% Lynx/2.8.5dev.7 libwww-FM/2.14 SSL-MM/1.4.1 OpenSSL/0.9.7 
15 14151 0.64% Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; YComp 5.0. 


Hope this helps.