I travel with a Nikon F3 but leave the motordrive at home. I take a 20mm f3.5 and an 80mm f2.8. Typically I shoot scenics which require a wider lens and I like the forced perspective it gives to groups and individuals as well as incredible depth of field. I take the 80 because it's nice for portrait shots and the occasional candid from across the camping area. Both are also incredibly light as opposed to a zoom and overall, they are sharper. If wildflowers are your thing, I'd take a macro lens if you have one as they are supposed to be especilly nice this year. The only time I've ever wished I'd taken a long lens, (a 180 f2.8 or 300 f2.8) was the 2 times I had a deer wander near camp, but the overall weight deters me. If you just want to magnify your vision I suggest a good pair of lightweight binoculars.
I seldom carry a flash as I prefer natural light abut I do have a small Braun unit if I feel I will need it. I carry a small table top tripod that helps with time exposures or group shots that I want to be in. I shoot 95% slide film (100 speed or slower) as it's better for stock sales. I usually shoot EPP 100 but am testing E-100 VS (very saturated) as the Kodak Rep was nice enought to send me 60 rolls last month. Nothing will ever beat Kodachrome 25 or 64 but it's just too hard to get processed. I shot 13 (36 exposure rolls in '96 and 8 in '98. Film is cheap compared with the cost of the trip so shoot alot. Also if you shoot slide film you might need to bracket exposures, whereas with print film there is usually no need to shoot more than one exposure.
Try to shoot alot early and late in the day as the light is always better than at mid day. Have the camera handy as shots are easily missed, but keep extra ziplocks around to protect things when afternoon rain storms persist.
Chris in Houston