In terms of calculating your IBR payments, I highly recommend the calculator at
http://www.ibrinfo.org/calculator.phpFiddle around with it and calculate the impact of your 403(b) or traditional IRA contributions. IBR considers your AGI, and 403(b) and traditional IRA contributions are pre-tax, so they lower your AGI and therefore your IBR payments. If you have the $$ to make retirement contributions, you might want to go for a plan that will reduce your AGI while you're on IBR -- but balance that against the benefits of contributing to a Roth (given your low tax bracket now, the benefit of contributing after-tax to your Roth might outweigh the benefit of reducing your payment by $25/month).
I agree that allowing the interest to capitalize at the end of your grace period isn't a terrible idea if you know (a) that you will be working FT for a qualifying agency/non-profit and (b) your AGI will never exceed the max allowed to qualify for IBR. On (b), you can calculate your max AGI if you play around with the IBR calculator, using the same loan info by changing your income. Keep in mind that it's your AGI, so you can ostensibly make more than it's going into your 403(b). Also, if you have children or a spouse (and file jointly), that will impact your repayment amount until IBR. Also re: (b), if at some point you don't qualify for IBR but it makes sense to continue on the PSLF track, then you can switch to a 10-year standard repayment amount and that will count towards PSLF. That payment is calculated using the amount of debt you graduated with, not the amount you carry when you switch.
Because your IBR payments will be $0 for the first year, if you will be working in qualifying employment, I recommend consolidating and going on IBR ASAP. That way, you will not waste any of those qualifying months. Also, your payments next year will be based on your 2013 taxes, in which your AGI reflects only 6 months or so of your salary (so, lower IBR payments for your second year as well).
The other reason to start the consolidation / IBR process ASAP after graduating is that it takes a long time. I would except 3 months for the consolidation and then they will screw up your IBR application so you will have to re-apply for IBR. In fact, I would just not apply for IBR when you consolidate because the loan servicer won't get the paperwork and will put you on standard anyway. So you might as well wait until your loan is assigned a servicer to apply for IBR, so you know where to send the IBR paperwork.