'Reckon' literally means to 'calculate', so if you say 'I reckon to get away by 2.30' or 'I reckon I'll get away by 2.30', it's what you expect will happen.
You've thought about all the things that need to be done before then, you've made a rough estimate of the time they'll take, and made a confident guess at 2.30. You're not 100% sure, but that is the time you expect to be able to get away.