WARNING
You shouldn't be fooling with the public beta UNLESS YOU ARE PROPERLY BACKED UP.
If you find you don't like, it's going to be difficult to "get back, get back, get back to where you once belonged" without a backup.
A better way to play:
Buy a cheap 2.5" SSD -- 128gb is all you need. $20 or so.
Get a USB3 2.5" enclosure like this:
Attention: package contains an extra foam sticker for 7 mm thickness hard drives, you should attach the sticker to the original one inside the lid before you insert the hard drive; 12.5 mm hard drives might be incompatible with this product. 70% faster than traditional USB 3.0 With UASP transfer ...
www.amazon.com
Now install the beta onto the EXTERNAL USB3 SSD.
It will boot and run quickly.
It will also leave your internal drive untouched.
So you can experiment with the new OS BEFORE you commit yourself to it.