You bet. You'll want to use the excli software profile update command (not the install command) to keep your custom Dell drivers. Download the patch bundle you want, upload it, and esxcli away!
The update option will leave your current drivers in place while the install option will overwrite everything with what's in the patch bundle.
Check this out for more info
http://www.v-front.de/2012/11/are-esxi-5x-patches-cumulative.html
All the best,
Mike
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Mike Brown
VMware, Cisco Data Center, and NetApp dude
Consulting Engineer
Twitter: @VirtuallyMikeB
Blog: http://VirtuallyMikeBrown.com
LinkedIn: http://LinkedIn.com/in/michaelbbrown