Compared to some games, Japanese Pokémon games could be said to be 'easy' to read the Japanese in, they only use hiragana and katakana (the two phonetic syllablaries) until BW, which you have an option to set it to include kanji (the pictographic characters). In that way you only ever have 100 or so characters to deal with instead of potentially thousands. I don't know any other languages but English and Japanese, so I can't really comment on learning Japanese as a second language compared to learning something else as a second language.

And yes. The only exception is BW, which you can't play non-English BW on non-local DSi/3DSes, but they still work fine on DSes worldwide. All five European languages are in the same local region though, so even if you have a UK 3DS, French and German would still work, though Japanese wouldn't.