The bus ride is about 5 minutes, and buses will arrive every 15-20 minutes. If you're at the bus stop at 1 you'll arrive in plenty of time. In my experience, you'll have to make a table request when you check in at the restaurant.
agree that you will have to ask when you check in, and may have to wait longer for a table if its really important to you. In case that potential extra wait would be an issue... We've sat a table or two back from the window as well, we weren't right up on the savannah but could still see plenty animals just fine.
Another option for viewing animals is visiting the resort's outside viewing area either before or after you eat. We were able to do it while we were waiting for our table. We didn't ask to sit by a window, and we were seated at a table one back from the windows. We could still see out the windows, although we kind of lost focus on that once the bread service came!
Agree with pixarprincess and ChristineOH, you don't need to be right at the windows to see the animals. We were two tables back with a good view and after our meal went outside to the obseration area. It was very peaceful with lots of giraffes to watch. Also, sitting a little further back, you don't have people "touring" your table during lunch/dinner.
We love Sanaa. Have a great time! Our first visit there a few years back we allotted 45 extra minutes from our 5pm ADR in case we needed to wait a bit longer for our table request after check-in. Figured we'd check out the lovely grounds out back in the interim. Surprisingly we were called 5-10 minutes later and seated at the center window table. Every single thing about the experience impressed us and we've gone back to Sanaa almost every trip since.
I recommend letting the host know it is your first time visiting Sanaa and you wouldn't mind waiting for a window table. That should do the trick! If you end up being seated right away, you can always go outside and explore after your meal.