15/20 dinars top (under £10), and you should be able to get it for less, especially if he puts the meter on. Make sure you hold on to your luggage when you leave the airport or the porters will grab it and expect a tip - they will also get a further tip from the taxi driver they steer you towards.

Greet the driver in Arabic 'sbarkhir' (good morning) or 'aslemma' (hello). Say where you want to go then add 'kadesh?' (how much?) Remember to fall about laughing at his first price whilst saying 'la, gahli barcha' (no, too expensive) You should eventually arrive at a price you are happy with. Remember you will need to have local currency which you can change at the airport.
Incidentally I've had a look at the exchange rate this morning and it does seem to have deteriorated quite a bit since I was out there in October. You can print off a currency converter below.
http://www.oanda.com/converter/travel
Hope you have a wonderful time.