Before you start

An unlocked handset, or an eSIM-capable one
A US address for postpaid, but not for prepaid
A payment method — prepaid accepts foreign cards, postpaid usually does not

Step-by-step

1
Activate an eSIM before flying, or buy prepaid on arrival
A US eSIM activates before you land so you have a working number immediately for rides, deliveries and bank verification codes. No identity registration is required at any point.
OnlineWho: YouDay 1
2
Check your handset is unlocked and band-compatible
Phones bought on contract abroad are frequently locked, and US band combinations trip up some regional models. With 3G shut down there is no fallback network to land on.
OnlineWho: You
3
Start prepaid rather than fighting a credit check
Postpaid runs a credit check. With no US file you will be declined or asked for a deposit. Prepaid has no check and is usually cheaper for the same data allowance.
OnlineWho: You
4
Enable Wireless Emergency Alerts and register for AlertOC
Federal wireless alerts cover evacuation and severe weather warnings automatically. Orange County also runs AlertOC, an opt-in county alert system that is far more granular and is what actually reaches you first in a canyon fire. Sign up for both in your first week.
Mobile appWho: YouWeek 1
5
Set your power account up with the city, not with Edison
Anaheim Public Utilities is the city's own electric and water utility and covers the whole city. Outage maps, high-bill alerts and payment arrangements all come from Anaheim rather than from the investor-owned utility serving the rest of the county. Register on the city's utility account portal in week one so outage notifications actually reach you.
OnlineWho: YouWeek 1
6
Prepare for a red-flag day in the canyons
Santa Ana wind events drive the region's worst fire weather, and Anaheim Hills sits in the wildland–urban interface. Keep a charged power bank, know your address's fire hazard severity zone on the state fire marshal's map, and remember that a home internet router without power takes your Wi-Fi calling with it.
OnlineWho: You
7
Port rather than cancel if you switch later
Number portability is a legal right and works between carriers and MVNOs. Request the port from the new carrier — never cancel the old service first, or you lose the number.
OnlineWho: You

Documents you’ll need

Passport for postpaid; nothing at all for prepaid
US address for postpaid
A payment card — prepaid usually accepts foreign cards, postpaid rarely does

Things most newcomers don’t know

Your utility is the city, which changes who you call and who alerts you.

Anaheim Public Utilities has run the city's electricity since 1894 and its water too, and it is the only municipal utility in Orange County. Every generic Southern California guide tells you to open a Southern California Edison account, which is simply wrong at an Anaheim address. It also means outage alerts, rebates and payment plans are city programmes — worth registering for in week one rather than during an outage.

Source: Anaheim Public Utilities

AlertOC reaches you before the federal alert does.

Wireless Emergency Alerts are broadcast to a wide area and fire only for serious, imminent threats. AlertOC is an opt-in county system that can target a specific canyon or street with an evacuation warning well before a federal alert would fire. In the hill neighbourhoods that lead time is the whole point.

Source: Orange County Health Care Agency / AlertOC

The credit check is the barrier, not the documentation.

Carriers check credit before offering postpaid, and a newcomer with no file gets declined or charged a deposit. Prepaid sidesteps it entirely and usually costs less for the same data.

Source: community-reported

The US has no SIM registration at all.

Most countries in this app require passport registration to activate a SIM. The US requires nothing whatsoever for prepaid — you can buy one in a supermarket and be online in minutes.

Source: FCC — consumer guides