This is something that I observe quite closely in fighters who pursue their career overseas. I look at someone like Manny and you can see that his English is at the same basic level it always seems to have been. Cotto on the other hand was someone who clearly didn't know very much beyond 'Hello' and 'Thank you' in his fight promotions and yet is now able to converse and put together fairly well constructed sentences and express himself with a great degree of clarity. You can see the progression over a few years and it always pleases me to see fighters make these kinds of linguistic progressions. On the other hand you get fighters like Mayorga who have never given a hoot about the whole process and that is fair enough too. However, I like to see a fighter make an attempt to become more mainstream by broadening their linguistic palate to some degree.
Cotto speaks better English than Roger Mayweather which says a lot. So, well done Cotto!