We had to pay $30blz departure tax and $7.50blz for some environmental fee. We got stung for $5blz per person for a fee that the border crossing people (behind the desk) conjured up. We only found out later and stupidly didn't get a receipt (usually a sign that something isn't legit). It's the price of 2 beers, so we'll get over it. We also had to pay 160 quetzals for the temporary vehicle permit. This has to be paid in quetzals, so if you didn't change up at home, you'll have to negotiate a rate with the touts outside. They only exchange US dollars or Belize dollars. They quoted us 7.3, then went to 7.4. The rate is currently $1usd to 8 quetzals, so that gives you an idea of their cut. We changed up what we immediately needed, then enough for food in the evening. NB We went to a bank the next day in Santa Elena and got a $1usd to 7.8 quetzals rate. 

That evening we drove to Tikal and told the guards at the entrance that we were staying at the Jungle Inn. Camping along the road or in the grounds is now forbidden, but for a small fee Jungle Inn offers camping and use of facilities (clean bathrooms, hot showers, free wi-fi).