Having tried mexican food all over switzerland, using some of the reviews of this forum as a guide, i am quite impressed by the food at Comelon burrito bar.
The owners run a tortilla company that sells to Manor and perhaps some other places and they finally opened a small storefront in the old town in Vevey, just off the marche. http://www.comelon.ch/
(they seem to have more info on their facebook page)
Prices are reasonable for switzerland (CHF 13.50/burrito, CHF 18 meal with chips and drink, or 9 to 11 for a quesadilla +4.5 for meal combo).
Mexico is a a big place with all kinds of regional food variations, and mexican food in the US has all sorts of different regional variations as well, but to me the flavors, concept and price of this place are really good and worth a try - especially after trying place after place over the past few years and being very disappointed. There are definitely aspects that aren't "authentic" but in the same way that a chipotle burrito isn't authentic either, but still tastes good (to me).
It has a similar vibe to burrito brothers or amigo taco in lausanne, but has more seating.
some downsides are the lunch only hours, potential for long lines at peak lunch time, limited menu and seating.