I will throw this out there for everyone, and then I am done. Now again, I don´t pay taxes in Portugal, but I do in the US, so add on probably another 30-40% to your budget.
My wife and I visit the US twice a year, and take about three to four trips around Europe each year, plus travel around Portugal about once monthly.
We live off of $4400 a month after taxes. And that includes Health insurance*. We have a 4-bedroom apartment on the edge of the historic Centro area. We don't have a car and rent one when we need to (2 days rental this weekend was $20, but gas, half a tank, and tolls will be $60-70).
*We prefer the quickness of using private hospitals for most routine procedures, plus we have two within a five-minute walk of us. Nothing wrong with the NHS other than it can take a long time to be seen. In a private hospital, you can schedule things almost immediately. After the first year here, you don´t need health insurance if you don´t want.