luohu station to laojie station

we (wife&I) will be in hong kong in feb 2013, and will be visiting shenzen for 2 days, and would like know how far (by train or cab) it is from luohu station to laojie station (roughly), as we would like to see dongmen pedestrian street. also, I have been advised that dongmen is not the safest place to visit. can someone please advise if normal security measures (money belt and secured bags) are sufficient? I would be most grateful