Partial Florida registration numbers.
Two of the counties in Tampa Bay Area have reported voter registration numbers (which closed Tuesday for the primary in a month). All these numbers are since Jan 1st.
In Pinellas County, the number of voters who switched from NPA (no party affiliation) to Democrat was 1,435. It's a safe bet most are Bernie supporters.
In Pinellas, switching from NPA to Republican was 1,263. I'm guessing that's mostly for Trump.
In Hillsborough Co., 895 switched from NPA to Dem, and 662 switched from NPA to Republican.
New voter registrations (all parties) in Pinellas:
4104 in 2016, compares to:
3131 in 2008, and:
3048 in 2012.
Don't have Hillsborough numbers for new registrations.
Leon County (Tallahassee) reports 2,000 NPAs have switched to either of the two parties, with most going to Democrats.
Info is from Tampa Bay Times article from yesterday. They also quoted elections officials as saying registrations and re registrations across the state are strong.
edit: Florida has a closed primary, which favors Clinton. Although the re registration numbers are high, and presumably mostly for Sanders, they're probably not high enough to make more than a dent in her lead.