Taxis here are quite a different experience here, better know some Spanish to communicate easier, either negotiate a fare if you know how much it should be by asking the staff at your hotel if starting from there, or others were you're starting from, or be on the meter.
When we first crossed the border by bus into Paraguay, the bus doesn't wait and took off. After having our passports' entry stamped, we hooked up with two others to share a taxi to the bus terminal to share the costs.
We arrived at the bus terminal bought our tickets for ASU - Asuncion for PYG30,000. We didn't find an ATM for the local currency. There are Cambios -currency exchangers but they'll give a poorer exchange rate. We came across another couple from the earlier bus to the border, after they got the passport entry stamped, they returned to the area where the bus let us off earlier and got on board the next bus going by/to the bus terminal and waived the bus ticket receipt and didn't have to pay again.
We again split the cost of another cab fare with another tourist visitor whom we met towards our hotel we selected from the Lonely Planet Guide. We went on speculation as we didn't have any reservations. Fortunately for us, they had room for us.
We were going to walk about and explore the city a bit but was warned by a hotel security person not to walk the way we were headed as it's not safe to walk in the parks at night and not to have valuables like cameras displayed. So we taxi to our destination by meter, but the driver couldn't read or understand the written destination and ran to someone else at the taxi stand to find out where we wanted to go, the meter indicated something like PYG8,000, but asked for considerably more than what the meter showed.
We taxi another time splitting the costs with some others we had been talking with at the Britannia Pub to go to Africa Disco for a negotiated PYG20,000 but when we arrived, the taxi driver wanted more but we only gave him the agreed to price.