The beer problem people are mentioning may be more connected to gluten than to alcohol. Gluten seems to be a big problem for a lot of people with MS, and several MS sites--like Ashton Embry's Direct-MS website--recommend going completely gluten free.
The Direct-MS site says beer, whiskey, and other malt beverages contain gluten. So you might want to avoid those.
My husband, who has MS, drinks wine with dinner on a regular basis. We're on a pretty restrictive diet, and we're pretty good at telling when he has an issue with a certain food. The wine doesn't seem to bother him at all. We're definitely moderate drinkers though.
Since we're believers in the diet connection, we avoid all the mixed drinks from bars/restaurants for fear of what crazy ingredients they put in the pre-packaged mix. But when we have a party or go on vacation, we make our own mojitos and margaritas (with 100% agave tequila) from scratch. I actually just posted a mojito recipe on my personal blog (http://multiplesclerosisrecipes.blogspot.com
). I'll try to post the margarita recipe we use, also. You can check it out if you want, but you can also probably just google for recipes. As a bonus, the homemade drinks actually taste much better