While the Android L Preview has thus far been limited to use on the Nexus 5 and the 2013 version of the Nexus 7 tablet, that limit has now been breached as some crafty individuals have gotten the preview of Android L to work successfully on the previous Nexus phone, the Nexus 4. If you own a Nexus 4 still and have been eager to try out the Android L Preview for yourself, now is your chance and there is even a handy little video that they uploaded to show just how everything works on the Nexus 4 so you can see that it's in good working condition. Just like with the Nexus 5 and Nexus 7 devices, it's important to remember that this is a "preview" version of the software build so there are going to be some bugs, that is the point. If you notice anything that doesn't work quite right don't be surprised.
You may be in no rush load on Android L especially if you'd rather wait for an official launch of the update, and that's completely OK as you'll get your chance later in the year when it releases. Yes, the Nexus 4 will reportedly be on the list of supported devices, however when it comes to Nexus phones that is as far back as it goes, which also shouldn't be a surprise since the Galaxy Nexus didn't get Kit Kat officially either.
If you want you chance at the preview and don't particularly care to wait for these kinds of things and are OK with the bugs that will undoubtedly show up as a result of loading on this software, than you can find all the instructions you need at the XDA link for the original thread below. We did post the video for you below so you can watch that as well which we absolutely recommended if you're moving forward with this. As always with anything of this nature, make sure to do a nice little backup of anything you want saved just in case, and it would be a great idea to make sure you have a backup of the system image should something go wrong.