Ooooer, where to start?
Okay, Conceicao is not in Tavira, it's about a 10 minute bus ride away and you are surrounded by low-rise apartments. And a lot of English, French and Irish tourists. And the prices in the bars on the front aren't cheap. If you go a couple of roads away from the front, it's cheaper. Conceicao is actually almost along the EN125 - main road - and you would have to take the little "train" down to Cabanas which is where you'd find the Ria Formosa- walking would take a long time, probably about half an hour or so. You would also need to either take the bus or train to Tavira.
Santa Luzia is a lovely place, quiet, but with some superb restaurants. Also not actually in Tavira but within walking ish distance. Not sure of buses though, I can always find out.
In Tavira itself, you do not need or want a car. You can walk everywhere - but beware - the calcadas (cobblestones) can be very wearing after a couple of hours
Also, don't go right on the river front bars and restaurants - again, they're expensive, as that's where the rich tourists go!! Go a road or two away and there are some lovely and very reasonable restaurants.
There are also some cheaper residencias - which bascially are bed and breakfast places. We stayed in a couple, which are fine for a quick break, but not so good for a week or so. Although in saying that, that was 15 years ago and there are some really good ones now.
Private villas are going to be expensive - again I can ask around, if you want.
Staying in Tavira, Grumpy and I would be more than happy to drive you around a few places as it's only 15 minutes drive away from us
Bluesue has stayed in the Vila Gale - make sure you have the one that is right in Tavira, the one up the road, by the railway line can be noisy at week-ends, as loads of Spanish use it for cheapo breaks - and apparently, they can be noisy!! A few friends have stayed at the one in the centre and have been very happy.
Anything else, give me a shout xx
Kaz has my e-mail, if you need anything x