im from california, but i have lived on the gold coast for 3 years and am quite close to surfers paradise actually.
i know where every bathroom is on the coast and there are lots. even toilets in public places like parks and the beach. pretty much everywhere. i have not had a problem anywhere going to the toilet. and there are nice comfy benches near the toilets for those with a partner or friends that need to sit and wait for you. as my husband knows well.
i've even had the pleasure >_< of using a toilet at a hotel or restaurant or 10 (heehee) without having to eat there or be a customer.
aussies are very laid back and these things are okay and nobody bats an eye.
sushi is not nearly as good as california as the only raw fish they serve is salmon and tuna. you will find a lot of so-called sushi being canned tuna salad or terriyaki chicken. i know, dont ask me. but they have lots of fish n chips shops that grill fresh fish. menus are quite diverse and you shouldnt have any issues with food.
have fun! its awesome over here. i love it!
and if you need to see a doctor, you dont need insurance and its only $35-$60 for a visit, and prescriptions are not bad either. seeing a specialist is a bit more spendy, but most doctors know what UC is and can prescribe for it if needed.
so you should be A-OK!