Areas with a rhotic accent include Barbados, India, Ireland, Scotland, Northumbria, southwest England, most of the northern United States (excluding New York and the New England region), and Canada.
Areas with a non-rhotic accent include Africa, most of the Carribean, most of England (especially Received Pronounciation speakers), Australia, New Zealand, South Africa, the southern United States, New England, New York and Wales.
What is the 'post-vocalic r', and can you give some pseudo-phonetic examples?