Europe is set to require tourist visas for American citizens in 2025. Details TBD, stay tuned.
Your passport needs to be valid for at least six months beyond your trip's end date. Some airlines may not allow you to board the flight if your passport doesn't meet this requirement.
Yes, outlets in Spain have different outlets and voltages than the U.S. These are called 'Type F' or 'Type C' outlets. Phone chargers, hair tools, etc., can quickly burn out without proper voltages. Be careful! We recommended purchasing these voltage converters (e.g., on Amazon).
It is not necessary, more of a personal preference. Hotels typically have WI-FI included and many cafes and restaurants will offer free WI-FI. If you opt to not pay for an international data plan, we recommend you download the City Mapper app which includes a map that is easy to use for directions around Palma, Mallorca.
Mallorca is extremely safe, but similar to other areas in Europe, the island has pick pocketers. Be sure to keep your valuables in your hotel safe or in your front pockets which are less accessible. Also, avoid placing your phone on a tables if your eating outside and hanging bags on the back of chairs in restaurants.