I will be deploying about 20 temperature sensors that are based off the arduino pro mini
My question is if they can be powered with 5v from a hacked up usb cable plugged into a usb adapter in the wall. If not is there anyway to power from the wall because I don't want to try and use batteries because they don't suit my application
Thanks for the help 
My question is if they can be powered with 5v from a hacked up usb cable plugged into a usb adapter in the wall.
If you hack it right. But, why? Just use a 7.2V wall wart.
BRiteBak:
I don't want to try and use batteries because they don't suit my application
I don't blame you. Batteries are a terrible nuisance and only used out of desperation.
Perhaps you should explain just which temperature sensors these are. In general however temperature sensors must not heat up as that would of course, completely invalidate their measurements, so by definition they use very little power indeed and you can power many from the Arduino supply.
Yes, you can supply 5V wallwart power to the VCC pin directly and bypass the onboard regulator.
PaulS:
My question is if they can be powered with 5v from a hacked up usb cable plugged into a usb adapter in the wall.
If you hack it right. But, why? Just use a 7.2V wall wart.
I can scab the usb wall sockets off people and cut up old mice and keyboards for the cables
CrossRoads:
Yes, you can supply 5V wallwart power to the VCC pin directly and bypass the onboard regulator.
Perfect, do I need to worry about the amps going in or use some sort of regulator to avoid burning it out?
The pro will take the current it needs.
Make sure the voltage is 5 volts, and observe the polarity.
Note, always follow the maximum pin current of 20ma or a total for the chip of I believe 150ma.
400mA for a SMD chip, as it has two VCC and two Gnd pins, and the limit is 200mA per pin.
20mA per IO, with limits per port per the notes in 29.2 of the datasheet.
@Crossroads, what page is that on?
CrossRoads:
400mA for a SMD chip, as it has two VCC and two Gnd pins, and the limit is 200mA per pin.
20mA per IO, with limits per port per the notes in 29.2 of the datasheet.
How can I regualte the amps? Do I need to or can I just hook it up to any charger and it will be fine?
You need to design the load on an output so it doesn't take more than 20ma.
If your o/p is driving a resistor load only and you need to have the full 20ma flow through it, then using ohms law:
(An o/p will go from 0V to 5V)
V/A=R 5/.02=250
Your resistor would need to be 250 ohms to get 20ma through it and therefore not damage the Arduino output.
Now you need to limit your load currents so the maximum package current does not exceed edit: 200ma.
Section 29 of the data sheet. I have posted several times now a direct answer from Atmel saying the 200mA is per VCC and GND pin. The notes in section 29 define the current limits per port. Any current above 20mA degrades the output (high output droops lower, low output rises higher).