Amalfi/Sorrento in April-how crowded?

It doesn’t matter. If you have never been, you will enjoy it regardless of crowds.
The end of April will be busy because of the weekends and holidays (Liberation Day on April 25 and Labor Day on May 1). Also near Easter week and Easter Monday (another national holiday) lots of people will be traveling everywhere. Just go and don’t worry about it. The only time the Amalfi Coast isn’t busy is when the weather is not too great, like in winter.

Hi, Giangilberto from Milan, just a couple of suggestions: april is considered mid-season rather than high season, so you’ll generally encounter fewer crowds than in july or august, for example.
Since the tourist season is just getting underway in spring, one potential issue is the reduced frequency of ferries connecting the various towns along the coast service is ramped up during the summer months. However, the spring flowers are in bloom, the weather is pleasantly warm, and the Mediterranean might be suitable for the season's first swim if temperatures are mild enough. Visiting in late spring or early summer also helps you avoid the massive tourist crowds of july and august, as well as the high temperatures later in the year.
As for Puglia, the situation is a bit different; in my view, the best way to enjoy this stunning region especially places like the Itria Valley is by car. You do need to pay close attention to ZTLs (Limited Traffic Zones) to avoid unpleasant surprises, I was actually speaking with a close friend from Locorotondo just yesterday, and she told me that, only a few days ago, she saw tourists driving into a ZTL without even realizing it and getting fined.

Above post from goingsouthminibus reported

If I was planning a trip with friends, and something was high on their list, then I would honor that. On our recent visit to Amalfi, we were told it is crowded year round, but April/May is a bit better than June, July, August. For fewer crowds while in Amalfi, you may want to consider a day trip to Ravello. I recommend you do not take the SITA bus, but instead, reserve a seat on the CMS shuttle bus.

We were in the AC three years ago in May, and Positano and Amalfi town were swamped with people. The towns were just not built for the hoards that invade them, either in spring or fall. In addition, there is no fast nor efficient mode for travelling about, so much of a one day trip would be spent in transport. The infrastructure has been sadly neglected for decades, it's not like getting around in areas north of the AC. The influencers don't post pix of the realities on the ground.
One viable option that folks here report is taking the fast train to Salerno, and finding lodging there, where it's not as crowded. You can then take ferries (weather dependent) to see the coastline. I wish we tried this route.
In any case, have a great trip!

Pat, this is exactly the information I was hoping to get from this board. When I visited I thought the Cinque Terre was gorgeous but the literal crowds of people swarming the trains and stations reminded me of the New York subway. I wish we had stayed somewhere else on the coast. I imagine late April around Amalfi would be as you described.

The Amalfi coast is almost always crowded and getting there can be a challenge. I've, for about a dozen years now, have always based myself in Sorrento. I took the bus once. Never again. "The" bus? Which bus? I had to wait for 3 before there was a seat available. Anyway, now I take the ferry. What amazing views! I usually book one that lets me get off in Positano for an hour or two and then takes me to Amalfi Town for a few more hours. I've found that taking the bus back from Amalfi Town isn't so bad - and I can get it to stop right in front of my hotel (il Nido), which is above Sorrento. Sorrento can be crowded, especially on the very narrow lanes in the old shopping area. But I've never found it offensively so. Sorrento is an amazing place for a daily passeggiata, shopping (love the linen shirts and inlaid wood), and the most beautiful sunsets! Several times once the sun has set, the people who have been watching in silence, break into applause. Gotta love Italy!

I was fine with my stay in Cetara, but it was nearly ten years ago and it seems the other villages are now getting many more visitors. But then you may have companions who want the full experience of Positano and Amalfi, which were take it or leave it for me—I only cared about the overall stunning nature of the area.
I’d see how the Puglia portion fleshes out—there are cliffs and scenic seaside over there, too!
(From someone who also found the crowds at CT dispiriting.)

nmdhoff, I suggest that you look at the vast number of posts here on the AC, using the Search box top center. There is just so much detail necessary to plan even a brief visit. Although I have little desire to return, I'd even suggest that "seeing" only one or two towns is not enough to fully say that you have "seen" Sorrento, the Amalfi Coast, Pompeii, the four other historic sites nearby, Naples, Capri, and so on.

Just to take the ferry example, it's not only necessary to make sure you have the correct (part of the year) ferry schedule to look at, but coming up with that schedule for a future visit is quite difficult. Since there are multiple ferry companies, research is even more difficult. Positano, a popular visit, has a smaller harbor and pier, so it takes smaller boats that are more likely to be cancelled on account of wind or wave activity on a given day. It's an article of faith here that "you HAVE to see XXXXXX from the water." Well, after multiple returns to Sorrento by water, I can say that it looks different from the water than from the land. My own related feeling is that the extra cost balcony and Vesuvius view from our bed in the (Sorrento) Ambasciatori was the best part of our visit - which included an eight-hour car and driver to "see the AC". We slept in Sorrento because it has the best transportation connections in that part of the (non Amalfi, rather Gulf of Naples) coast.

It is often impossible to wake up in this area and fly out of Rome the same day.