Download Google Maps offline before you leave. Open Google Maps → search "Zürich" → swipe right on the place card → Download offline map. Covers navigation, transit, and business search even with zero signal.
Check your US carrier plan first. T-Mobile includes free international data and texting on most plans (5–15 GB high-speed, then unlimited at slower speeds). AT&T offers an International Day Pass for $12/day. Verizon's TravelPass is $10/day. If your plan already covers Switzerland, you may not need anything else.
Consider an eSIM if your carrier charges for roaming. An eSIM is a virtual SIM you install before departure — no physical card needed. Providers like Airalo, Holafly, and Saily offer Switzerland plans from ~$4. Holafly has unlimited data; Airalo is pay-per-GB and cheaper for light usage. Install and test the eSIM on Wi-Fi before your trip.
eSIM compatibility: iPhone XS and newer, most Samsung Galaxy S20+ and newer, and Google Pixel 3+ all support eSIM. Check Settings → Cellular → Add eSIM to confirm your phone supports it.
Wi-Fi is widely available. The Marriott offers free Wi-Fi for Bonvoy members. Most restaurants, museums, and Zürich HB train station have free Wi-Fi. Use hotel Wi-Fi for heavy downloads and save cellular data for on-the-go navigation.
Also download Google Translate's German pack for offline use. Camera mode translates menus and signs in real-time without data.
Turn off cellular data on your physical SIM if using an eSIM or relying on Wi-Fi only. Accidental roaming on a US carrier without an international plan can cost $2–10/MB.