QUE GRANDE JURENA! 
Quedo asi:
Código PHP:
SELECT cl.country, cl.region, cl.city, cl.postalCode, cl.latitude, cl.longitude, cl.metroCode, cl.areaCode FROM CityLocation cl
INNER JOIN
(SELECT locId FROM CityBlocks WHERE ($ip > startIpNum AND $ip < endIpNum) ORDER BY startIpNum DESC LIMIT 1) t1 ON cl.locid = t1.locId
