As you might already know, in Mexico, water from the tap is not the preferred beverage of most folks. Most people in Mexico don't drink the tap water and as a traveler you are advised not to drink tap water. Why?
The water might be tainted mostly due to pollution from above the ground that leaks into the cracks through old waterlines.
I've read that the government is making more of an effort to improve the water quality, however, many residents are still skeptical and continue to drink bottled water only.
I guess I can't blame them. Nobody wants to get sick.
So to be on the safe side, be sure not to drink Mexico water from the tap, or you might end up with a case of traveler's diarrhea or indigestion.
Most restaurants and good Guadalajara hotels will provide you with bottled water during your stay. If you want water when you are in the restaurant be sure to ask for (Agua purificada).
Bottled water is sold everywhere, so don't be worried. You can't walk a block without running into a little store (tiendas) selling water, juices, sodas and much more.
You might think that I'm a bit paranoid but on my very first trip to Guadalajara, Mexico (November 2004) I even used bottled water to brush my teeth.
I had been preparing for my Guadalajara vacation and reading up on lots of travel books on Mexico and quite a few suggested it. Yes, it may sound crazy and Antonio told me I was overdoing it. But I didn't care. It put me at ease and guess what? I didn't get sick!
Now I'm not making any promises. You just have to be careful of what you decide to put in your stomach.
Watching out for what you eat is also extremely important.. Most people are more likely to get sick from contaminated food than from the water. Read more about Montezuma's Revenge.
So remember that Mexico water from the tap is not for drinking. There are many stores and people always selling bottled water so there is no reason for you to go thirsty.
And you'll need to drink plenty of liquids with all the attractions in Guadalajara that you'll be seeing.