Where Van Signal Actually Drops on the Costa Vicentina
The Costa Vicentina is the one part of mainland Portugal where van internet genuinely fails, and it fails in a predictable pattern: fine in the towns, gone on the roads between them. If you know where the gaps are, they cost you nothing. If you do not, you will find them at exactly the wrong moment, which is usually at a trailhead with no downloaded map.
This is the detail we left out of the campervan and motorhome WiFi guide, because it only matters if you are actually driving this coast.
The pattern, not the map
We are not going to publish a coverage map with green and red blobs on it, because those maps are always slightly wrong and go out of date quietly. What holds up is the pattern.
Towns are fine. Aljezur, Odeceixe, Carrapateira, Vila do Bispo and Sagres all have workable 4G in the built-up part. You can take a call, upload photos, do the banking.
The roads between them are not. The N120 and the N268 run inland of the cliffs through low hills and river valleys. Signal comes and goes on a scale of a few kilometres. It is rarely a long outage; it is a lot of short ones, which is worse for anything streaming and irrelevant for anything cached.
The beach access roads are the real gap. Almost every good beach here is at the end of a dead-end track that drops off the plateau. Praia da Amoreira, Monte Clérigo, Arrifana, Bordeira, Amado, Castelejo. The car park at the bottom is often the worst signal for kilometres, because you have just put a cliff between yourself and everything.
Why here specifically
The Parque Natural do Sudoeste Alentejano e Costa Vicentina covers a long, thin strip of this coastline, and building inside a natural park is restricted. That includes masts. The coverage you are getting is largely coming from inland, reaching over.
Then the terrain does the rest. This is not open country like the Alentejo plain, where a mast covers a long way. It is a plateau cut by deep valleys, and you spend a lot of your time either below the cliff line or inside a valley. Both put rock between you and the transmitter.
The southern Algarve has neither constraint, which is why the Algarve connectivity picture reads so differently to this one despite being an hour away.
Three fixes that cost nothing
Download before you leave town. Offline maps for the whole Odemira-to-Sagres stretch, not just today's leg. Do it over coffee in Aljezur while you have four bars, not at the top of the track down to Arrifana. This single habit removes most of the problem.
Move the router, not the van. If you are running a pocket WiFi, get it onto the dashboard, a window shelf, or hung near a skylight. A van is a small metal box, and the difference between a router in a drawer under a metal-framed bed and the same router on the dash is routinely the difference between nothing and a usable connection. Try that before concluding the car park has no coverage.
Do the connected things in town. Not a technical fix, a scheduling one, and the one experienced vanlifers actually use. Calls, uploads, admin and route planning happen where the signal is. The cliff car park is for the part of the trip that does not need the internet, which is most of it.
What we would actually rent for this coast
Honestly, it depends who is in the van.
One person, two weeks, phone only: buy an unlimited eSIM. It is cheaper, there is nothing to return, and out here it will find exactly the same signal a hotspot would.
Two or more people, a laptop that has to work, or a long stay: rent the pocket WiFi. It runs 6 to 8 hours on its own battery and charges while in use, so plugged into the van's 12V socket it simply stays on. It covers up to 10 devices on one connection, which is the part per-person eSIM plans cannot do. From 18 EUR for three days, and the daily rate falls the longer you keep it.
The honest caveat is the one thing no rental fixes: on this coast you are buying a better tool for the signal that exists, not more signal. Everywhere else in Portugal, that distinction stops mattering, and it is worth remembering that the Costa Vicentina is the exception on a network that is otherwise very good.
If your route continues north up the coast or inland, the road trip internet guide covers tolls and navigation, and the coverage map overview has the rest of the country region by region.