I am wondering whether it makes sense to see Chengde end Oct. or weather will be too cold already?

Yes, you can pay a visit at the end of October. It will be cloudy and rain lightly sometimes. The temperature will range from 25F to 50F. You should pack jackets, sweaters, shirts, pants, sneakers, and raincoats.

I am afraid that the leaves may have fallen by then. The best time to enjoy the changing leaves is from mid September to mid October.

You can take a bus to CD from Sihui Bus Station, about 6 miles (10km) from Dongzhimen. Take metro line 2 from Dongzhimen to Jianguomen Station, and switch to metro line 1 to Sihui Station, Exit A. Upon arrival, take a bus to CD. The buses are available from 6:30 to 19:10, and the fare is CNY 85. The trip takes about 3 hours. :)

Thank you!