I just got back from San Diego/LA and would like to provide some insights into the Airalo eSim.
TL;DR version: it works, but you need to make sure your phone is compatible.
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Hardware: I have an iPhone 11. AFAIK, all iPhones 11 and higher have a regular SIM and an eSIM slot, so you should be good to go. My brother has an Android phone (can't remember the brand, but it's about 2 years old) and he did NOT have the slot. He ended up giving the Airalo eSIM to his wife (who has an iPhone) and bought a T-Mobile SIM to use instead.
eSIM: I got the 5GB/30 day package ($16 USD) since we were in the States for 9 days and I wasn't sure how much data everyone would use via hotspotting.
Setup: Airalo has some pretty good instructions on how to add the eSIM, so I won't repeat here. On the iPhone, you can label your phone plans, so I would recommend using names that are easy to pick out. Once you have the eSIM set up and topped up, you can, in theory, turn on the cellular plan as nothing will happen until you make it active for Cellular Data.
Speaking of which, make sure you have data roaming turned off for your regular carrier. That way, if you accidentally switch over, you won't get dinged for roaming.
Before I switched to Airplane mode on the flight, I turned my Cellular Data off. So basically no data for either SIM. When we landed at LAX, I switched out of Airplane mode, and set the Cellular Data to Airalo (with Data Roaming), while keeping the Voice Line with my usual carrier. It did take a few minutes to kick in, but once it did, I got connected to the T-Mobile network.
Usage: I will say that despite using my mobile all the time and hotspotting for the kids, we only burned through 1.5 GB. Still, better to pay the extra $5 and overestimate instead of getting throttled.
I used Waze to go everywhere with no issues. The kids looking up... whatever they were looking up via the hotspot had no issues as well. Similarly, my wife was able to easily retrieve her emails via the hotspot. There were some dead zones on the beach, and Catalina Island was very spotty (probably due to the high volume of cruisers that had a port day), but overall I think this was successful.
Phone: The phone, however, was hit and miss. I think that, because I was not in the "home" area of Canada, the calls were taking some time to get through. I did find that things were better using wifi calling and/or iMessage. so consider using your data to make calls.
Conclusion: I think this worked out great for us, and I'm going to try this again in a few weeks when I head down to Cleveland for a few days. Again, it's imperative that you ensure that you have one regular SIM slot and an eSIM slot. If you do, I think this is a great option to use.