I don't think there is a need to be offended. A lot of Americans don't have a grasp of their own language, let alone another and it is very surprising for them to see someone from a third world country speak it so well.

Now, regarding speaking in English, I guess it really depends on you. Language is a means of communication. If you feel it's way easier communicating something in English then go for it, especially in writing. Because my written Nepali is terrible, I almost always write in English. But there is one huge exception. I have seen a lot of Nepalis who will try to use English just to show off in verbal communication. If a Nepali speaks to me in Nepali, I will talk in Nepali.

IMHO, I think it is very very very rude to converse in English when your countrymen is repeatedly talking in Nepali. I've had encounters with some of these too-cool-to-speak-Nepali folks who would constantly talk to me in English. I feel if someone speaks to me in Nepali, I develop a different bond altogether. English lacks certain words and expressions that are often used in colloquial Nepali.

FF