about 3 days
you can eat very cheap, o, your money will last longer if you go up to kuala lumpur though, or somewhere in malaysia anyway
johor is not a very nice place, according to here.
i think its about myr$6 to the uk gbp. about half that for the sgd$
sgd$10 a meal will fill your tum, and yes, you can eat healthy too, ie, avoid the fried rice, or fried noodle, or the fried queh pisang (fried bananas)
you can go and buy some fresh greens at ntuc fairprice, go to delifrance and get some bread rolls, and make your self some sandwiches.
or, if you don't mind getting a bit "fat" you can eat:
fried rice with red skin pork
fried bread (murtabak/channai) with curry sauce
satay
fried noodles
soup noodles
roasted pork
fish head curry
nasi lemak
soft shell crab
ais kachang
chendol
kaya bread (kaya is egg jam)
bottle of water would set you back about sgd$1.50 per litre bottle
travel around the city, $10 stored value card can last you 3 days, of course the more you travel, the more the balance will drop. if you use the mrt, the prices depend on how long you stay on the lines. buses, it depends on how far you travel, $1.50 to $2 is the max per air cond bus trip
hostel, the best according to what i have read on their website, is the inn crowd at sgd$18 per dorm bed per night.
4 to 5 days is about right.
its about $2 or so to get the sbs transit #170 bus to larkin, and then a bit more to get up to say, malacca town.
if you go to www.xe.com and do a forex comparison, you will see you get more myr$ than sgd$ for your uk gbp.