Take 39 and transfer to 853 
(Nah ... jkjk ...)
The waiting time for 58 is pathetic, from Bishan. Not sure from
Pasir Ris though. Also 58 goes all the way down to Paya Lebar
before going back to Pasir Ris, 53 just takes the TPE.
So my choice is definately 53 =).
Hope to see you in Orientation next year ... I hope to be your OGL
then 
(Urrr ... Speaking about the backdoor gates ... I thought it's
always unlocked? If one is spoilt at least walk for a minute more
to another backgate)