Most of the jungle lodges will charge between $25 - $35 to take you into SI town so it may not be that much of a savings to book a Tikal tour from an independent tour operator over the hotel's tour. Some tour ops from SI will pick you up at one of the lodges but again with a surcharge (for all the reasons Simon listed above). You can do Tikal on your own by taking a taxi to the border and a taxi or mini van on the Guat side for about $75 pp. Doesn't really get much cheaper than that. Transfers from the airport to most of the jungle lodges run about $100 for 1-4 people (some places more, some a bit less depending on the lodge). The only "remote" jungle lodge with A/C is Jaguar Paw but they are quite far from the border, thus Tikal, and I do not think they offer tours there. For A/C in the SI area, you are looking at SI Hotel, Cahal Pech Village & Windy Hill. They are all in or on the outskirts of town. May can be hot - depends on where you are from if you need A/C - if you are used to hot & humid, you may not. It is typically pretty breezy in the Cayo mountains.