Just got back from Puerto Rico. I spent a lot of time going around the San Juan metro area, predominantly in Viejo San Juan, Santurce, Isla Verde, and a short stop in University Gardens.
T-Mobile's network still performs as well today as it did when I last tested and in my opinion is the best on the island. n41 is still at 100MHz in most areas though I did record a few areas with only 80MHz. Yesterday the FCC announced that they're finally granting T-Mobile their Auction 108 winnings so we'll probably finally see that increase. They also have 15MHz of n25 and 15MHz of n25 and 15MHz n71. The fastest speed I recorded while there was 922 down and 120 up, presumably aggregating n41+n25 and potentially n71 as well but I wasn't able to confirm that. A couple of things I noticed about their network are that their is a ton of split-sector n25 deployed in San Juan, much like in the U.S. I even noticed some n41 sites that had 4 or more sectors. The weirdest being the site on top of SJU Airport where they have 6 n41 sectors each broadcasting 80MHz of n41.
AT&T SIMs roam on LIberty's network but they still treat it as the home network. In my opinion they're the second best network in Puerto Rico. Liberty is still using the AT&T MCC-MNC code and is pretty much coasting on AT&T's network upgrades. They have 10MHz n5 virtually everywhere but I never saw my phone connect to any other 5G bands. Their saving grace was just how much spectrum they have to aggregate across midband and lowband. I'd see combos like 10MHz n5 + 20MHz B2 + 10MHz B66 + 10MHz Band 30 + 5MHz Band 2 and get upwards of 200Mbps. Coverage was slightly worse than T-Mobile in my experience, even indoors which is a surprise given T-Mobile usually struggles a bit indoors due to their macro density.
Verizon is roaming on Claro in Puerto Rico just as they have been for years. No idea if there is 5G roaming because I was connected to LTE the entire time. Toggling 5G didn't do anything and both pings and speeds weren't great. Speeds were in the 20-40Mbps range consistently and pings over 200ms. For comparison T-Mobile's pings are in the teens and Liberty pings are in the 40's even when roaming using an AT&T SIM. Claro's network is ok in my experience with nothing really notable about it.
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Here are some pics of sites that I took: