You can get a smattering of meaning, but all the subtleties are lost.

Even Galician, which is half-way between Portuguese and Castilian Spanish, is tough to follow.

Especially listening to spoken Portuguese and even more so Brazilian Portuguese. It almost sound Slavic!
(English native speaker here but a language major)

European Portuguese is the harder of the 2 and the one that has a bit of a slavic sound. Brazilian sounds much more like Spanish.

Nasals, of the same sort.

Many of the same kinds of affrication and lenition.

(Although the vowel reduction's much more like Sorbian.)

understand it spoken, and the Portuguese I read wasn't demanding.

The first time occurred when I was going around the room checking the notes and outlines of students in my college composition class to help them before they started writing their essays.

One young woman had a very Spanish name, so although I knew she was from Brazil, I thought Spanish might be her first language.

When I picked up her notebook from her desk she said, "Sorry! My notes aren't in English." I glanced at them briefly and said, "No problem. I can read them. And I did. But after getting several lines down the page, I realized they weren't in Spanish, either, but in Portuguese.

Since I had no trouble reading them, I went ahead and finished reading two and a half pages of notes plus an outline in Portuguese.

For the entire semester, her notes and outlines were in Portuguese, but I never had trouble reading them.

BTW, I am nowhere near fluent in Spanish. Even back then, when not as rusty as I am now, I had lost my speaking/listening skill from lack of practice, and my reading skill in Spanish was also pretty rusty, though still not useless.

But they’re not as close as one would think. Spanish is much easier to understand.

Have no real interest going to Brazil though, but do want to visit Portugal in the near future.

Hard to fit in when I'm also studying several other languages.

quite fluent in Spanish and one quite functional, though not fluent, had no trouble at all understanding and being understood when visiting Italy. Each did two study-abroads, and when their semesters were over traveled around Europe, including Italy.

My son had wanted to study Italian rather than Spanish, but I insisted on Spanish because it's such an important language in the world today, and because Spanish and Italian are mutually intelligible, as I discovered as a young woman when I had no trouble using my (then much better) Spanish to follow Italian conversations among my Sicilian grandmother and her friends.

My son forgave me for pushing him to take Spanish. He fell in love with Spain on his first study-abroad and ended up majoring in Spanish and international studies, becoming so fluent in Spanish that native speakers always assume he's a native speaker from a different Spanish speaking country.

We went to Italy at the end of September and not only did I understand much of what Italians were saying, but many of them understood and spoke Spanish. It did help bridge the gap.

Our last taxi driver apologized, “No English” and I replied, “Io, solo inglese e spagnolo.” He then spoke to me in fluent Spanish. He asked at one point in Spanish, “Does your husband understand Spanish?” and when I told him no, he replied, “All the better!”

And Italian and French.