Hi Seth,
Provided your client has legitimate physical offices and unique local phone numbers at each of the 6 locations, there is nothing spammy about having a unique page on the site for each office and connecting those up with your Google Places/+ profiles.
There is no reason to put these on subdomains. This structure is fine:
www.lawyers.com/divorce-lawyer-san-francisco
The challenge is to create unique, valuable content for each of those pages. If you take a cookie cutter approach, then that does end up looking spammy, but if care is invested in making the content different on each of the pages, this is an excellent enhancement to your ability to rank well for each city. Let's kick some ideas around.
Keyword+City A
On this page, you've got 400 words of unique text, plus testimonials from 10 local clients in City A
Keyword+City B
On this page, you've got 600 words of unique text, plus 3 videos
Keyword+ City C
You take an FAQ approach to this page, giving great answers to the top 20 question clients who are considering divorce want answers to.
Keyword+ City D
You create an infographic detailing the typical steps in the divorce process, from filing for divorce to being granted divorce. You add text testimonials from 15 clients in city B.
Etc...This is just an off-the-top-of-my-head example of planning the content strategy so that each page is offering something different. You will plan this more carefully. What will be the same on each of these pages is a unique opening sales statement (unique for each page) and the complete NAP (name, address, phone number) for each office. Work with the designer to create a cool way to format the opening statement and NAP so that visitors hitting these landing pages know they've just been invited to call the divorce lawyer in city X, before you get on to the other data on the page, such as detailed copywriting, videos, infographics, etc.
My advice, basically, is to take the most creative possible approach to these client scenarios. Educate the client that the more he invests in these city landing page (in terms of creativity, time and funding) the better his chances of dominating in the SERPs.
Hope this helps!