Dear UCSF Mike;
Prior to having both my knees surgically altered to have ruptured cartiledge removed and for some time after I did average that much in exercise or physical therapy walking of at least an hour a day in the evenings after work in the Hood of the Outer and Inner Avenues back and forth down to Arguello and back. A good solid hours worth. The ruptured cartiledge did not happen from walking but from much much much earlier more stressful events - keep walking - today not quite as much maybe half as much -
The unease Deerek experienced brought about by the transients and the homeless in and around the Ocean Beach Safeway for me is a moot - mute - mutt (eh?) point as I have not seen that many at any time - one or two max - even including the guy hanging near the Safeway doorway asking for change - the guy might rotate but the certainly don't congregate - and they are not there every day - and as a general rule they know better not to hassle anyone around the Safeway.
Have you considered carrying a broom stick(s) - used - ahem - of course as a walking stick or those walking sticks hikers use as they strut along the trails - as a non-deadly weapon - of which I am certain Chris can point out a course or two you could take - like Kendo - the Japanese sword fighting with bamboo sticks - Aiii Yah!
If there are self -defense courses which can teach the elderly to use their canes as self-defense weapons - you certainly could use broom handles or the walking sticks as self-defense weapons. Nothing like a walking stick speared into someone's eye to make a point to move on to an easier target.
Ewwwww - so blood thirsty - but all's fair in love and war and what ever it takes to beat a mugger is total war.
Play the what if game - what if I was walking down the street and something came up and what would I do if ... Plan your plan ahead of time then the mind can go to plan 1 - 2- 3 ... and react accordingly
Or get one of those collapsible steel batons there are self-training videos available on how to use them effectively - but this may be defined as a CDW!!! So carry it openly!!!
Or there is always pepper spray - mace spray - wildfire spray
Mace and Pepper Spray are non-lethal weapons that can now be carried in the State of California without a permit, if used solely for self-defense. [California Penal Code section:12403.7(a)] In California, the largest can of pepper spray you are legally allowed to carry is 2.5 oz.
Or there are stun guns - or better yet air tasers which fire projectiles then zap!!!
You protect You the best way You need to protect You
BTW: How about them Niners - won two games in a row!!! Super Bowl here we come!!!