Pee away. I had my wettie for 3 seasons before it blew out in the bicep area in December 2011 while freediving for crays. I can safely say I pissed in it almost every sesh and it never smelt or had any 'acid' degradation.
As for taking care, well I use to take it into the shower with me at home after my session and rinse it well and then leave it to drip dry in the shower. Then when ever I would remember I would just hang it up outside in a shady spot that got the breeze. Hanging out in direct sunlight for long periods of time is sure to cause some UV damage over the lifetime of the wettie.
On a side note, pulled into Trigg this morning on my way home from a morning work call out. If I had a wettie I would have gone in. Despite how rarely I use them I am starting to get sick of being frozen stiff in the surf. Getting too many cramps