In short: yes. It is considered safe to travel to both Cabo San Lucas and San Jose del Cabo. Violent events haved plagued Mexico for quite some time leading the United States to issue a Level 2 Travel Advisory for the entire country of Mexico. This means that they recommend visitors exercise increased caution due to crime and kidnapping. However, the majority of the occurrences have involved locals and not tourists.
The good news is that Baja California Sur – the state Los Cabos is in – is not included in the travel advisory. At the time of this post [February 2020], travelers were advised to reconsider travel to other states like Mexico [which houses Mexico city].
For reference, the United States currently lists over 70 countries with a level 2 travel advisory. The extensive list includes super popular tourist destinations like Italy, Spain, Costa Rica, Belgium, and even the United Kingdom. If those places are not questioned, we should not need to ask “Is Cabo San Lucas safe?”.