Portuguese: like Spanish, but quite different

We've been spending a few days in Portugal, before the usual English family Christmas. Porto and Lisbon are both fine cities to visit: narrow, winding, steep cobbled streets, many petering out in vertiginous stairways; old churches dripping with gold leaf and ornate carvings; blue and white azulejo tiles, either abstract or painted with naturalistic historical scenes; grand and gracious squares and avenues; decadent pastry stores on every street corner. Oh, and lots of vegetarian and vegan restaurants for some reason.
I've been particularly interested, though, in the Portuguese language. I speak pretty good Spanish, so I thought, well, Portuguese is very similar, isn't it? How hard can it be? It turns out that, yes, Portuguese is pretty similar to Spanish in many ways, but it's also quite different in others.
The most immediate difference when listening to a conversation in Portuguese is all the shush-shush-shushing, from a hard zzhh to a soft sssssh. But there are several ways in which Portuguese is similar but not quite the same as Spanish. It seems that there has been some kind of consonant shift at some point in Iberian history. Many words using an n in Spanish, for example, use an m in Portuguese (e.g. Spanish una, Portuguese uma; Spanish Don, Portuguese Dom; Spanish bien, Portuguese bem). Except that some n's become o's (e.g. San in Spanish, São in Portuguese; racion in Spanish, ração in Portuguese). Spanish l's often become Portuguese r's (e.g. Spanish plaza, Portuguese praça), ñ becomes nh (e.g. baño/bahno; señor/senhor), ll becomes lh (e.g. batalla/batalha; campaña/campanha) or ch (e.g. llegada/chegada); etc.
To confuse things further, some Portuguese words sound the same as Spanish, but turn out to be spelled differently (e.g. t before e is pronounced as ch: e.g. Portuguese leite is pronounced lay-chay, like the Spanish leche). But some Portuguese consonants are pronounced differently for no apparent reason at all (e.g. verde is pronounced, at least sometimes, vair-jay).
So, Portuguese: like Spanish, but not like Spanish. And have I mastered it? Have I hell! Often, a carefully-constructed, painfully-practised sentence elicits nothing more than a smooth response in perfect idiomatic English. It has been a surprise that pretty much everyone speaks English, at least in tourist towns like Porto and Lisbon. And you know, after the first day, like most pampered English speakers, I'm just fine with that.