Just been going through the receipts from self and GF's visit to Portugal last year - in 14 days we spent @ 550 euros on eating out (around £467 at the time...).
Couple of evening meals came from local convenience stores, but most were taken in cafes or restaurants with three being over the 40 euro mark for two (Terra and Lost In in Lisbon and the Pousada in Sagres) and two over 35 euros for two (D'Italia in Sagres and Ristorante Da Vinci in Lisbon).
Rest were below 30 euros for two by eating from the specials menus (especially if a beer was part of the deal) on an evening). Couple of quiche, a beer, coffee and fruit juice in Sintra was 12.75 euros. 2 pastel aria, 2 double espressos and 2 fruit juices were 8 euros in Lisbon. Mini market meal in SIntra was 10 euros for bag of bread rolls, cheese slices, some salami, a cold drink and two 250ml cartons of red wine. Beer around 1.50 in a cafe, coffee around 1.20...
Other advice? Good walking shoes or sandals for Lisbon... ear plugs for sleeping, especially at weekends, get a reusable water bottle and keep filling it to save on buying bottled water. If you're planning on using buses, Metro or trams in Lisbon (or for a side trip to Sintra for example), get a travel card and load it up with the cost of a few trips.
Do some research into which places offer free admission on Sundays and if you're planning on going on Tram 28 in Lisbon, go early in the morning and be prepared to comment loudly if someone tries to push past you in the queue!
Other suggestions? Buy the paper versions of the respective guidebooks (even if they're older editions if you've already sorted out accommodation) and copy suitable pages on destinations (or cannibalise the books if they're old ones) and take these with you as reference pointers.
Printed pages easier to read in a cafe or on the street and less obvious than pulling out an iPad or other tablet (and you don't need to charge them up either!). We didn't take smartphones, tablets or laptops with us last year and didn't miss them either.
We travelled light (hand luggage only @ 6kg - people with the biggest bags all under 25!), did wash and wear on the clothes and bought anything we ran out of or needed at the last minute in a local pharmacy or a supermarket... Travelling light and no wheelie bags paid dividends and earned up lots of envious looks from those with big bags.
If you're getting a train in Portugal, don't leave it to the last minute to buy your tickets. We booked ours in advance a day or more before travelling and were pleased that we did when we saw the queues for tickets at Lagos railway station (and there was only one window open for ticket sales).
We bought our advance tickets at Rossio station in Lisbon - the ticket office was on the concourse next to Starbucks or at Tavira railway station Tickets for travel to Sintra came out of the machine and if you're heading there, there's a day ticket available that will give you bus travel between the various palaces around the town. ..
If you're wanting to leave luggage in Lisbon, there are various sized lockers on the platform level at Rossi station near the hostel on that floor. Oh, and we didn't have any problems in finding ATMs during our visit.
Hope that this helps out - enjoy!
