I'm sure it would be grammatically correct. After all, in speech you often decide things as you speak, and the "not" may end up after the "to be". However "to be not" doesn't sound nearly so good as "not to be", probably because the word "unsafe" ("said to be unsafe for travel") is available, and also to be not safe for travel makes it sound like "not safe for travel" is a quote of someone else (extracted from their saying "it is not safe to travel") whereas "to be unsafe for travel" is natural as one's own words.
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Anonymoussaid not to be safe to travelMy choice would be ... said to be unsafe for travel.