Logic would dictate that it is a far better idea to bike home after drinking than to drive home.
It's not exactly the best idea, for obvious reasons, but it is still an alternative that demonstrates foresight and advanced planning when a designated driver is not available.
It's also illegal. Cycling under the influence (CUI) is a misdemeanor criminal offense here in sunny California. The worst part is, there's no set blood alcohol concentration that triggers a CUI.
The law regarding biking under the influence vaguely prohibits riding "while under the influence of an alcoholic beverage or under the combined influence of alcohol and any drug."
There are two things you should note about that sentence. One, it merely says "under the influence". That means drunk, tipsy, or possibly even one drink in, depending on the reasonableness of the cop that stops you. Second, it says either alcohol or a combination of alcohol and a drug. Presumably, that means simply being higher than a kite on some illicit substance, such as bath salts, would not be sufficient for a CUI charge.
Disclaimer: We are in no way advocating the use of drugs, before, during, or after cycling. Or at any time, really.
So, based on this law, an officer does not need to obtain blood or breath evidence of alcohol consumption to arrest you. They merely need objective evidence, such as failed field sobriety tests, alcohol on the breath, or a flushed face.
If that sounds like an unfair law that is ripe for abuse, well, you're probably right. However, the good news is that the punishment is merely a $250 fine. It is, however, a misdemeanor criminal offense that will stay on your record, so you might consider walking home from the bars next time.
If you are a severely unlucky person who happens to get caught, there are a couple of things you can do. The law allows you to request a blood, breath, or urine test to contest the officer's assertion that you were drunk biking. If you request it, the officer must comply.
Also, the law prohibits drunk biking on a public highway, which includes streets and sidewalks but does not include private driveways and streets not open to the public, such as in private gated residential communities.