If I spend most of my time outside the house walking dogs, can I still use the portion of the time I spend in my home office as a deduction for home office?

[JulieR]

Yes. If you are self-employed, you can claim a deduction for home office expenses if you use a portion of your home exclusively for business.  It doesn't matter how much time you spend in the "exclusive use" space during your working hours so long as that space is used exclusively for the business.