you'll be fine but you'll want to take motorbike taxi to go from your place to Nana BTS station cuz it's a bit far and streets are packed full of stalls at night there so not easy to walk.
Also you don't see it but on their map
http://bangkok-sukhumvit.frasershosp...cation_map.gif
where soi Nana crosses water there's a express boat stop, giving you good access to interesting part of the city
http://en.wikipedia.org/wiki/Khlong_...p_Express_Boat