Poor you, thats so stressful...I had high BP after both my dds were born, and was on medication both times (expected, the second time, but was harder to get under control initially - then went down faster).
The first time it took about 8 weeks, the second time about 5-6 weeks, so not as long as you - but I was on a fairly hefty dose of medication the second time around. Are you on meds? How high is high, for you?
It is important for them to get a clear picture, because if you need meds they usually like to start you on them under supervision...to get the dosage right, etc.
I found the whole process really scary the first time around, and stressful (3 yr old and newborn...) the second time around. I did go back in both times, a few days after first getting home - real pita, but worth it.
I'm fine now, but doctors have warned me I will probalby have raised BP and need meds when I'm older - probably in my 60s or 70s. Something to keep an eye on.