You shouldn't bet on that.
The time zone on the receiver is set based on the Service Address on the account. The Topic Starter could change the Service Address to an Eastern Time Zone address to change the time zone on the Wally, but that would also change the time zone setting on any other receivers on the same account.
When you say you are getting the wrong guide data, is it the data for the previously scanned locals (wrong market) or for a wrong channel from the current market? I have seen both problems before. If the guide data for old locals (no longer scanned in) is still showing up on the wrong channels, then like HipKat said earlier, that should resolve itself but it may take awhile. Leaving the Wally in standby and letting it take a fresh guide download may help, but you may still have to wait until after the scheduled daily reset (or longer) for the guide data to start getting mapped correctly.
On the other hand, if the guide data that is showing up is for a different channel in the same market, then that is likely an issue with Dish's OTA guide database, and there is nothing you can do on your end to fix it. This is usually caused when two local channels start sharing the same frequency, and Dish's database cannot map the guide correctly to each channel. To use an example from my market (Cleveland, Ohio) WRLM virtual channel 47 now shares the same frequency as WEAO virtual channel 49. Since both virtual channels are in the same stream, they now have the same Transport Stream ID (TSID). Dish's guide mapping database only looks for the TSID and subchannel number (-01 in this case) to map the guide data, ignoring the different primary channel numbers (47 vs. 49). The host station is WEAO, so this issue causes the guide data for 049-01 to get mapped to both 047-01 and 049-01.