I'm about to buy two of the Lectrosonics ZS-LRLT L Series Wireless Systems, with the LT transmitter.

I'm in the U.S. These two will be on shoots all over the country. How do I choose which frequency bands to get?

Should they be the same band or different bands? We will have two people on camera, using both sets at the same time.

Many thanks.

Why don't you contact the nice folks at Lectro. If you ask nice, you can probably even speak to the (newly retired) president Larry..
PS- I would not call on April 1st..

also I think there are regional blocks and chart for that, the new L series is great and covers 3 blocks in one set.

Get in touch with the folks at Lectro, they can refer you to a chart similar to this.
http://www.lectrosonics.com/US/images/PDFs/RF-Analysis.pdf

They will be able to tell you what blocks would be the best to use in your area.

Word is, the 600 Mhz range might be sold off soon, so that will be no good, in addition to the 700 Mhz range which is already illegal.

HOWEVER, many sound guys are still using their old illegal gear with no issues. They tell me it depends where you are. . .a small shoot at an office building or wherever is one thing, sporting events or the like where they have a billion different audio people and guys with scanners walking around checking is quite another.

Yes, 600 Mhz range will be up for auction this year if the FCC does not postpone it (again).

FWIW, Back in days when we used the VHS fixed frequency systems (Lectro 185/187) There was what was known as a "traveling frequencies, (around 169.600 MHz as I recall) where there were no TV channels.
With the new Lectro's three block frequency span, I don't finding an open slot would be difficult. Naturally one still wants to scan each new location.

Thanks, Guys. Getting them ordered today.