Todd you should be good with the HCX Vista or Dakota or Oregon series. The Newer GPS's will pick up under really heavy foliage, trees, some parts of canyons and in houses. I'm probably venturing to say you should have no issues with the new chip set, even the dakota picks up more sats than my HCX but both will work in heavy coverage just fine.
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Failure is not an option!
USMC Jungle Environmental Survival Training PI 1985