L.A.
Downtown Austin has lights all the way down Congress Avenue. At the State Capital there is also a large Christmas tree.
On 37th Street and Guadalupe there is a neighborhood that lights the whole street. We used to walk the neighborhood and then go to Amy's ice cream for a snack.
The Premier event in Austin at Christmas time is in Zilker Park. The Worlds tallest man made Christmas tree is there. Also the "Trail of Lights" is amazing with tens of thousands of lights. They have a yule log, all kinds of performances and Santa is there.. Best of all. All of these things are free!
here is link. http://www.ci.austin.tx.us/tol/ Take a shuttle. they drop you off and then pick you up in front. There is a small charge to ride. We used to go with a group of families and sing Christmas Carols to get the whole bus to sing!
Remember to dress warmly and be prepared to walk. Also opening weekend to any of these events are really busy, so plan ahead and go in a good mood!