Petitioners would need 42,500 signatures in 30 days to get the recall on the ballot against the mayor (25% of turnout). However, turnout is much lower in the city council seats, so that may be only 2,500 or so signatures (depending on the district).
Of further interest is the second part of this point -- that you can mail petitions directly to voters and have it returned. That seems quite different from most other states laws.
Gathering petition signatures has become a sophisticated undertaking. Sometimes when politicos launch petition drives they hire people to gather signatures in public places, but that causes trouble because many signers turn out to be ineligible. Another method -- mailing petitions directly to targeted registered voters with return envelopes – has proven more reliable.