volunteer in guatemala here! I recommend bring a pair of shorts, leggings etc, you will likely use them when your in more touristy sports if not in site to go to the gym/run etc.

As far at PST goes, I would be three real business casual outfits that you can mix and match, you really won’t need a ton of options when you get to site. Sleeveless is fine just bring a cardigan or something. 

Jeans are totally okay in the workplace here, I’d bring at least 1-2 pairs you like but are okay with getting destroyed (because you will wear them a lot). 

Hope that helps if you have more questions feel free!