The current requirement is to have a passport starting January 2008 in order to return back to the USA when traveling by land from Mexico, that date may change.
There is a new bill in congress to delay this requirement to January 2009 due in large part to the extreme backlog of passport requests that is currently being experienced. The bill was voted on and the delay was overwhelmingly passed in the House of Representatives. The next step is to gain approval by the Senate and this is expected to be passed in the Senate as well.
The delay is a good thing for Rocky Point travel. Many travelers have been placed in the current backlog and invite the delay so their travel plans are not hindered. When the Senate vote is final, we will be sure to post an update to this requirement.