Not from the given reports... I think your best bet is to partition your HD with about 8GB and put it on there, then boot from it. Follow the steps for installing on a flash drive and do that instead.
Can I make a temporary partition on my SSD, install/update to El Capitan, and once finished, can I delete that partition? I really don't want to buy a USB adaptor just for this.
Got to agree with the last poster: get the adapter. If $20 is too much, I found a few on eBay that were like $12 but you have to wait longer for shipping. If you're neat an Apple store, spend the $22.00 (plus tax) and get one. Just my opinion though.
Can I make a temporary partition on my SSD, install/update to El Capitan, and once finished, can I delete that partition? I really don't want to buy a USB adaptor just for this.
Yes, create a second partition, install 10.11 to the second partition and you should be good to go. Delete the second partition when you are done. Your primary partition will not be disturbed.