The current communication paths being used with the MERs are described concisely in this piece:

"The vast majority of science data is being returned to the mission team on Earth through the rovers' UHF antenna, which communicates with the orbiters. Mars Odyssey has returned an incredible 85 percent (76 Megabits) of the data generated by both rovers. Odyssey's sister spacecraft, Mars Global Surveyor has returned eight percent (6 Megabits). Four percent (3 Megabits) of the data was returned through the X-band link direct to Earth."

Note carefully the ground based back-up system.

"The orbiters, with their more capable X-band communications systems, can transmit data back to Earth at a faster rate. This high performance is critical, as time on the large antennas here on Earth that were built to receive the data (the Deep Space Network) is limited given all of the spacecraft that rely on them."

Another passage mentions 10 minute windows per orbit when the MERs can transmit data to Odyssey or Mars Global Surveyor.

Clearly, if the Allen Array could be used, then no only would the MERs be able to transmit more data, Mars Odyssey would, and Mars Global Surveyor would as well.

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