Cash is king. Exchange fees are generally not charged. This way you will arrive in Mexico with pesos for cab fare to your hotel. Generally speaking, tip as you would back home. The water in Puerto Vallarta is one of the best in all of Mexico, and purified water is used extensively in hotels and restaurants.
Bottled water is readily available and inexpensive.
Use caution regarding ice in drinks, and produce washed in tap water, unless they are offered in major tourist-oriented hotels and restaurants. In general stay away from the street food booths. Puerto Vallarta is on Central Time, the same time as Texas. That's two hour ahead of Los Angeles, and one hour behind New York. The Mexican long-distance phone service, Ladatel, has phones in many hotels and downtown streets that allow you to make calls on your credit card.