Without refering to Flake-Gutierrez specifically, DHS Secretary Michael Chertoff reiterated his support for "guest" worker scheme:

"[The new laws should] bring them out, register them ... and make sure as a condition that they pay their debt to society for having broken the law... What I'm talking about is a common sense policy... We have to be tough. We have to be humane. We have to put into place a workable policy into this vexing issue."

"We" also have to do our job, and Chertoff isn't doing his. If he wants to advocate for an amnesty, he should quit his current position and go to work for the AILA or EPIC.

From this:

The Reform Institute and We Care America today called on Congress to show leadership on immigration. "Inaction on fixing the nation’s broken immigration system can no longer be tolerated. Congress must act on comprehensive immigration reform now," said Cecilia Martinez, Executive Director of The Reform Institute.

...Dr. Juan Hernandez, Senior Fellow of the Reform Institute's Comprehensive Immigration Reform Initiative, is available to comment on immigration policy. Dr. Hernandez served as Director of the Office for Mexicans Living Abroad under Vicente Fox. His recent book, The New American Pioneers, is an authoritative look at the complex issues related to Mexican immigration.

And, according to this, Eric Gutierrez of MALDEF ("Mexican American Legal Defense and Educational Fund") says that group supports the bill. And, the American Nursery & Landscape Association (ANLA) "applauds" the bill [1], saying among other things:

"The inclusion of AgJOBS in the STRIVE Act highlights the unique needs of agriculture," said Craig Regelbrugge, ANLA’s vice president of government relations and research. "The time for Congress to engage in this issue is now. Our industry, along with the rest of labor intensive agriculture, is at a labor shortage breaking point that Congress must address this year."

[1] landscapemanagement.net/landscape/article/articleDetail.jsp?id=413918