You shouldn´t have any problem in playing your English games on the Spanish Wii. Also you can configure the Wii to spanish. The WiiSports comes in English (voices + text) and if you put your Wii in Spanish, only the text will change to Spanish.
The region is the same.
The only thing which might give you problems is the TV. Althought I am not sure 100%. I remember when my sister left the UK, She gave here VCR and TV to me and I needed to make some changes because it seemed that the frequency was different. But then again, that was 10 years ago.....
But if you connect it to a monitor, it is OK.