Tucson's advantages are below-average cost of living (low gas prices, food, etc); airport and all services; lots of parks: city, county and federal lands to visit around the city; Mexican food. Many conservation NGOs are based in Tucson and I know GreenLatinos would attract a great pool of people from the region. We are close to the US-Mexico border and in past conferences I have run field trips to the border, which are very popular. May can be hot for some people, but it's still a time for activities outdoors and with an indoors conference it wouldn't be a big deal. I've organized and attended many conferences at DoubleTree Hotel - if you're looking for a contact, ask for Janet Hare. El Conquistador definitely has the capacity, and a great scenic location and facilities, but hard to walk out for food. Another one where other groups organize events is Ramada Tucson. It's not the best location (next to the highway), but lots of big events happen there because they have the space and capacity. There are other hotels on the same street, a park and places to eat close by. Westward Look is a nice hotel, but I'm not sure they can fit 250 people. The Tucson Convention Center is a place like that, but I'm afraid the cost would be prohibitive. I don't know for sure.