If you're after no-frills, fuss free accommodation in Portugal, you might want to consider a guesthouse / bed and breakfast, or alojamento local as they are known locally. Typically smaller than hotels, these often have a more homely feel, although they will usually have limited facilities on offer. Where a guest house might lack in amenities such as spa, gym, or concierge, it will often make up for in charm and character.
Since the facilities on offer may vary widely, it's vital that you do some research to ensure that your chosen lodgings have the amenities you can't do without.
Guesthouses may not offer breakfast and might not have a restaurant on site. If this is the case with the one you choose, you'd need to ensure that it's within reasonable distance of restaurants or cafes.
Guests with mobility needs will need to be aware that not every alojamento local will cater for these. ¬†In addition en suite bathrooms are not a given, so you would need to be prepared to share bathroom facilities.
What you can get in a guest house is accommodation that's typically more budget-friendly than a hotel. If you choose well, you might find a place that's in the perfect location; for example, a few steps away from the beach, or very close to the tourist attractions you want to visit. On the other hand, you'll need to study the map well to make sure you don't choose a guest house that's miles away from the places you'll be visiting.
In your search for the right kind of room, some Portuguese vocabulary might help: a room with two single beds is a quarto duplo, while a room with a double bed is a quarto casal. A room for one is a quarto solteiro.