In the current world of communication, where everythign is done via phone/fax/fedex, location should not matter. If you find someone reputed locally that's good, otherwise good attorneys anywhere in the US can help filing your case. Filing PERM is very critical and important issue especially when you can't afford denial due to lack of knowldge when you are in 4+ yrs of your H1B. Think carefully, don't go for money. Rajiv Khanna and Sheela Murthy are the reputed ones I know. Ultimately it's up to you, some people do the process on their own, you can choose that if you are confident about your knowledge.