Picking a Travel Agency

Hi there! I am preparing for my first travel assignment, but I'm having difficulty picking which travel agency to work with? There seems to be sooooo many to choose from, any suggestions/recommendations would be greatly appreciated!!
I am a Canadian RN, with 5 years working experience in Obstetrics, pediatrics, and med/surg. I'm looking to go to a warm sunny state, close to a beach if possible
Thanks again!