Cannabis Culture, which is not exactly required reading for most immigration attorneys, notes a report suggesting that "a suspected undocumented immigrant convicted of possessing pot may be more likely to face immigration detention than one who’s been convicted of rape." The report is from the Center on Juvenile and Criminal Justice, a non-profit and non-partisan organization whose mission is to reduce society’s reliance on incarceration as a solution to social problems. The center reviewed data on requests by ICE to law enforcement agencies to detain adult suspected undocumented immigrants. Salon has a take here including a response from ICE:

...ICE told Salon that because the report “only focuses on detainers issued on convicted criminals,” it “fails to recognize the issuance of ICE detainers on other public safety threats such as transnational criminal street gang members, international fugitives, human rights violators, national security threats and those who repeatedly violate our immigration laws.” The agency argued that the report “does not take into account detainers placed on immigration law violators charged with serious crimes who have not yet been convicted of a crime in the United States,” and noted that some people detained are ultimately released.

You can read the report in PDF here. The report also notes that "traffic offenders are more likely to be booked into ICE detention (75.8 percent) than violent offenders (67.5 percent)."