Question: is it legal to take a street sign

Answer: No, In most jurisdictions, the theft of traffic signage is treated like any other theft with respect to prosecution and sentencing. If, however, the theft leads to an injury, then the thieves may be found criminally liable for the injury as well, provided that an injury of that sort was a foreseeable consequence of such a theft. In one notable United States case, three people were found guilty of manslaughter for stealing a stop sign and thereby causing a deadly collision. This was publicized in the novel Driver's Ed by Caroline B. Cooney.