The hotel is not near Dongmen, it is near Luohu Boarder, you can take subway to Dongmen Area. Dongmen Area has several markets, Xinbaima is one of them. The price depends on what kind of clothes you want to buy and weather you are in wholesale or just buy several ones for yourself, generally it would cost no more thab 20 RMB for a pair of jeans, of course with not very good quality.

Hi Ms Jess,
I am staying at Perthden right now!(it is not a commonly known hotel I have found) I went to Dongmen a couple of days ago. It is quite close. You catch the number 1 bus at Lowu bus Station (just a few minutes walk away). It is our first time here too so I am just learning and it is very tricky!

Thanks For The Help... :)
Really Helpful :)