I have seen bienvenue followed by à, sur, and chez, and there may be others which I have not yet seen. When should each of these be used, and what other options are there, if any?
- Chez: used if followed by a noun owning the designated location (Bienvenue chez le coiffeur)
- Sur: used if you're on (sur) the location. Same goes for in (dans : Bienvenue dans la Matrice) and so on.
- En: used if the location is a region/country/etc with a feminine name that is not an island (Bienvenue en France [LA France]) or masculine name starting with a vowel or non-aspirated consonant (en Hollande)
- À: used if the location is:
- other regions/countries/etc with a masculine name (will most likely be au in this case, I can't think of one where it is à) or islands (Bienvenue au Canada/à Madagascar)
- or a proper noun/a designation of a unique place (in the context of the current discussion) (Bienvenue à Paris/au restaurant dont je t'ai parlé)
Those are not academic rules, just my two cents.
thanks to PapaPoule for the clarification on feminine/masculine names for regions/countries
thanks to Circeus for the clarification about island names