I've got an eTrex and I find its pretty good.
Standing outside It works fine. Heavy bush cuts the signal down a bit, but Ive found it better than friends Magellans in our gum trees (Australia) The Pine Plantations seem to cut the signal to a greater degree. The Pine needles seem to play up with GPS, Cell phones and radio signals.
On the dash of my car, once I found that it had problems locking on. I found that having AA batteries sitting next to the GPS on the dash interferred with the signal and the unit had problems recieving. Took me a while to work that out. I think the round bodies of the batteries reflected the signal too much. But as soon as I moved the batteries away, it locked on pretty quick.
I live at around 37 Degrees South. I've also noticed that my eTrex locks on faster when further North (towards the Equator so for you it would be South) It seems that in the Southern Hemisphere at least, it can lock onto more satelites faster the closer you get to the equator.