Travel / Holiday in Poland advice? Sights, some photography, look around etc. [4]

Hey there! I'm an 18-year-old female student, and I'm interested in visiting Poland maybe over this summer. I'm British, but don't worry, I'm not going to get plastered and start tearing the place apart! My friends want me to go to Ibiza instead (just guess the reason!), but I don't fancy spending all my time in a foreign country totally off my face.

Anyway, I'm primarily interested in seeing the sights, doing some photography, having a look round etc.

Sooooooo.. my questions are:

- Should I go alone, or travel with a friend?
- What mode of transport? Bus? Train?
- How is Poland expense-wise? Is it an expensive place to travel in?
- Any dangers I should know of?
- How friendly are you guys? People over here in London can be pretty terse with strangers, especially foreigners. ;_;
- How many people speak English? Will it be a problem if I don't speak Polish (other than a few guidebook phrases)?

Also, any recommendations of which city or town to visit would be great, or any specific things I should see.

Thanks a lot in advance for your help. <3