You mean when you upload them to the website or when you download them from the website to your computer?
Assuming you mean the first, then I'll start with the ordering. Ordering is by date. If you look at your gallery then the photos that come first are those with the most recent date. You can change the order by changing the date. So you can actually upload photos a year later and still have them show at the bottom if in reality the photos were taken long before.
To be honest, ordering is not the best way to 'group' photos. Then you'd be better of tagging all the photos you want to group together with the same tag. For example, this link shows all your photos tagged 'semuc', ordered by date (as always). You can essentially create endless numbers of customized grouped galleries around tags. All your photos with people, certain names etc. etc.
Regarding assigning a location to a photo, it is possible to do this by town, but unfortunately our current database only holds 2 million or so unique towns. So a lot of smaller places aren't defined when trying to enter them... hence going back to country for those. If you'd want to drill those down later on you could manually map them to a town using the mapping link. This is far from ideal and actually already being worked on, but part of a larger update, so I am not sure when it will be going live.