I cannot urge you strongly enough to read the websites which I've linked below. I'm sure you are a terrific person and a fine writer, but somebody new to the business trying to get their screenplay read has basically painted "TARGET" all over themselves in red paint...
Your local phone book will have local agents, SAG is for actors, I doubt reputable agents run around looking at telephone poles or laundromat boards, and I'm glad models have agents but models and screenwriters are two different things. Follow that advice and at best you'll end up unproduced; at worst paying somebody money to do something they're not qualified to do, as a result of which you're broke, your script is stolen, and your fledgling career is over. Thus the Association of Authors Representatives (first link)--read what it has to say!
Second: movies are made in L.A. Deals are made in L.A. and N.Y. Therefore, you want an agent in one of those places. Further: you want an agent who has contacts in the industry, knows how movie deals (which are as much legal as creative) are made and can make them, and is not primarily in business to take advantage of you. The Writers Guild of America represents screenwriters; the link below is a list of agents who are signatory to Writers Guild contracts, and are licensed in California.
Finally: before you do anything, register your script with the Writers Guild. Nobody in Hollywood will so much as touch an envelope where they could possibly, now or in the future, be sued for stealing the contents. (Be prepared to indemnify everybody...) Go to "register your script" on the third link for info. In fact, read the whole WGA website--if you really want to write screenplays, this is where you'll live.
Oh, and I get 10% of everything you make if you follow my advice...good luck!