nathank

basically you can't do a whole lot more without training AT altitude...

anything to improve your fitness (cardio/lung capacity effectiveness) will help, but the other adaptations the body only makes when exposed to altitude for specific durations of time. it is called acclimatization and is why on big mountain climbing expeditions climbers spend anywhere from 1 day to 2 weeks at high altitudes in preparation for a big climb. many physiological adaptations occur like increasing the number of oxygen-carrying cell in the blood. long term (people who spend YEARS at altitude) the body can make even more adaptations.

for training at "home" at low elevation there's not a lot you can do. some big-time athletes use "high altitude simulation" techniques which basically have lower pressure/and or lower oxygen content through some special chamber of mask. but for whatever reason these techniques seem to be of relatively little help --- probably b/c the adaptations come not just from training time, but from living at altitude - when sleeping, eating, etc. so you'd need to spend all your time for 2-3 weeks in a chamber or wear a mask 24/7. plus they are VERY expensive.

so basically you can:
1) try some expensive training method that probably won't help much
2) at the beginning of your trip add on extra time for acclimitization - 2 days to 2 weeks (but unless you have lots of vacation probably not an ideal solution)
3) continue to train like you did, maybe just more and just be as healthy and fit as possible and just deal with the altitude.

of course there are things you can do to minimize the effects of altitude: keep hydrated, get lots of sleep and eat well - basically give your body every advantage. plus there are some medicines but i wouldn't recommend any unless you're doing extreme stuff at >4000m (13000ft) - and most have risks/side effects.