Can I wear shorts and shirt

Of course

Yes that is fine

Yes. Most people wore quick dry shorts and t-shirt, some wear swimsuit. When I went out was cold. Some people were walking around in bathrobe and hanging bathrobe next to pond. Each pond has place to hang your towels, bathrobe and flip-flops.

Yes

Yes. There was a guest wearing yoga pants and a hoodie and several women in shorts and tank tops.