Generally ESLs can understand English decently, especially when an ESL version is spoken by another ESL. Their first languages needn't be the same, but it would help even more.
Between the english-speaking community, however, it has a derogatory meaning.
Damn, i got an ESL in my group. This is gonna suck...
Zip it, you'll be lucky if you contributed half as much as him, assuming he knows what's expected of him.
b.: Nah, I quit playing online games last january.