I've been flaoting the Frio since I could get in the water without drowning...my family has camped on the river at least anually since the 1930's.
If the river is way up, as long as it is running clear, it will be floatable, but some of the bigger rapids could be a little more intimidating than usual, to the point of being dangerous for weak swimmers in a few places. One thing is for sure, the trip will be a LOT faster than usual. It is best to float the river after a rain and rise in the river, as soon as it runs really clear, as it will be up a foot or so still.
At concan, it usually runs 1-2 feet, with 1 foot more typical. If it is running 5 feet at that gauge, like it shows on the river gauges on the web, it is probably a brown torrent full of debris still...but if the rain lets up, maybe Saturday afternoon would be a great day to tube it once the water goes back down some.
Floating it while it is running high and brown is plain stupid....