My groceries tend to be the same as the US; I don't buy a lot from the market, so we get most of our shopping done at PriceSmart to find more American food (PriceSmart is like CostCo or Sam's Club).
We personally live in housing provided for us and we don't own a car here yet, so I can't help you with those. Taxes are not very high (social security, retirement, and our guard fees are basically all that's taken out) and since this will be our first full year here starting this year, we won't have to pay any taxes back in the US next tax season.
To give you an idea, my husband and I are successfully living on about 700 USD/month (with very minimal travelling right now).