For better or for worse, English has become the lingua franca or 'common tongue' of scientific communication. If you want to be a successful scientist, it would benefit you to speak and write in excellent English.
This problem is not just about non-native English speakers. Many people who grew up in the U.S., for example, may not write or speak effectively in what linguists call "American Standard English\. What matters is that, if you are doing significant research, you should hope to communicate that research effectively to broad audiences. If you butcher grammar and spelling in a proposal, who is to say that you will do any better when you try to communicate your results to the scientific community? A proposal should 'put your best foot forward'. A poorly-communicated proposal suggests that you will communicate your research results just as poorly, and that the investment in the research may be questionable...regardless of how good the actual research may be on its own merits. Perhaps most importantly, if you can't explain your research well using English, reviewers of your proposal can't know whether or not your proposal has merit.
Everyone needs help in one way or another. I find it very relevant that some of the best research is co-located with educational institutions. Where we teach knowledge, we also discover it. Research organizations should be trying very hard to enable everyone involved to do their best. Several foreign-born scientists working in America have asked me to copy-edit their journal submissions or grant proposals, for spelling, grammar, style, and even scientific content. This is definitely the right kind of thing to ask of your friends. If you don't have such friends, asking nice people to help you with copy-editing or pronunciation can be a way to make friends.
Your professional success may depend on it.
The author's affiliation with The MITRE Corporation is provided for identification purposes only, and is not intended to convey or imply MITRE's concurrence with, or support for, the positions, opinions or viewpoints expressed by the author.