The highest tourist destinations reach heights above 3,100 m 10,170 ft and altitude sickness is a possibility.
In the winter months the park is extremely cold and it is necessary to dress warmly. Having said that, in the winter sunshine you could possibly strip down to a t-shirt in the bright winter sun shine - in the shade you'll need to layer up again however!
Chinese tourists dread standing in line and there is a lot of pushing and shoving getting on and off buses. Make sure you don't get pushed in front of an oncoming bus. Crowded trails can also be dangerous and if you walk on the edge of a path it is likely a shoulder or elbow with push you off. To really enjoy your time in the park you should walk on the trails on the opposite side of the lakes from the roads. These trails have considerable less tourists and you can really experience the serenity of the national park there.
English is not widely spoken in Juizhaigou.