Details follow, but broadly speaking, the picture is positive if you're in any kind of settlement, one way or another - but experiences vary hugely, partly based on networks (and people often don't like to shop around, so can get locked in...=
Firstly - for clarity, because terminology can be different - there are two main options:
1 - Broadband, generally referred to here as fibra, redes de alta velocidade, ADSL
You can check pretty accurate details of coverage, using a property's postcode, on the sites of the three providers, Vodafone, MEO and NOS (NOWO exists in some areas, too). They may need you to put in a phone number, which is a little annoying... There is also this map, which shows the main hubs:
and it seems broadly right.
In simple terms, fibre broadband tends to cover the centres of communities, and may not cover outlying villages, suburbs, and almost certaintly won't touch remote properties. Whilst some people moan about being prepared to pay €xx per month, the costs of expanding coverage are not justifiable by the income from 1 or 2 people, so the rapid expansion is likely still to focus on cities, towns and villages, not remote settlements.
Where you do have fibre, speeds are mostly dictated by the package you choose, which will itself vary by coverage. We've found, for example, that Vodafone is very consistent in providing what it says, starting at 100 Mbps and going up to 1 Gbps and beyond
However, the next bit may help.
2 - Mobile data, often unhelpfully called "banda larga", accessed using hotspots
This is the usual solution here, if you're not on broadband. Some rural communities have excellent data coverage (note that this is not always the same as mobile coverage, you can have better data than voice...) with speeds in excess of 30 Mbps which is great for Netflix, home working (even for companies with special software), etc.
Your friend for this is here:
It's maintained by the Communications Regulator, and its traffic light system is helpful. It's helped people we know, as you can pretty much tell exactly where is good, bad or indifferent.
Vodafone has just recently started doing a €15 for 15 days for unlimited data on their Hotspot (which costs around €45-50, sometimes with some data/days thrown in). If you have a good signal, this is very competitive.