oh don't do it- I used Greyhound when I travelled across the US- back in the mid 90's.
it was an unremittingly awful experience each and every time- they lost baggage each time I had to switch bus, they stop at every tin pot town along the way, they're noisy and uncomfortable, the bus stops are always in the most horrible parts of town, the journeys take longer than they would by almost any other means (including donkey cart- which would have been more comfortable)... and then there were the other passengers- the less said about most of them the better
if PT is the other choice I would use Amtrak if you can- I did one journey on Amtrak and it was so much better
$3.80 might seem expensive, count your lucky stars you don't live in the UK where it's nearer $9 a gallon