It's 3-4 hrs from Bishkek to Almaty by road in a shared car (tons available at either end, it's a very popular route, was $10 so/per person with my bad negotiation skills) including the boarder crossing (now improved from when I was there in '09) so very doable - there's just not much to see or do in either city, really, the countryside is what's great. The crossing on the east end of the Issykul has less traffic but's possible as well if you'd like to loop around - the scenery/hiking are long the lake are nice, just west of the IssykKul Lake Song-Kul is gorgeous for horseriding and relaxing in a yurt.