All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
First of all, you should know that the first thing a person should be called to is to testify that None has the right to be worshipped but Allaah and that Muhammad is the Messenger of Allaah . So whoever accepts this and embraces Islam, he is obliged to perform the prayer and then the other pillars of Islam. The evidence about this is that the Prophet clarified this order when he sent Mu'aath Ibn Jabal, may Allah be pleased with him, to Yemen and told him: "Indeed you will come across the people of the Book, so the first thing to call them to, is to believe in the Oneness of Allaah, if they acknowledge this fact inform them that Allaah ordained them to perform five daily prayers. If they perform the prayers, then inform them that Allaah commanded them to pay Zakat (obligatory charity), which should be taken from the rich and given to the poor, if they acknowledge that, take the Zakat from them, but do not choose from the best of their wealth." [Al-Bukhari and Muslim]. So whoever embraces Islam is obliged to perform the prayer which is the greatest obligation after the two testimonies of faith. As regards whoever is persecuted and is not able to show his religious rites like the prayer, then he should perform the prayer secretly as the companions used to do when they were persecuted in Makkah. It is reported that when 'Asr prayer was due, they would scatter in the land and perform the prayer individually. [Al-Haakim]. It is also confirmed that they used to go out while it was still dark [in the morning] and they would perform ablution and [Fajr] prayer. [Al-Haakim]. Besides, there are other narrations which prove that they used to hide their Islam and prayed secretly. The Prophet did not give them permission to abandon the prayer. Nonetheless, whoever is not able to show his religious rites is obliged to migrate. Allaah Says (what means): {O My servants who have believed, indeed My earth is spacious, so worship only Me.}[Quran 29:56]. Al-Qurtubi said: ''This verse was revealed to incite the believers in Makkah to migrate. So Allaah informed them that His Earth is vast and that staying in one place while being harmed by the non-Muslims is not acceptable.'' However, it is not permissible to abandon the prayers because of being persecuted. Had anyone deserved to be exempted from performing the prayers, the Mujahidoon [the fighters in the battle field for Allaah's Cause] would have been exempted, on the contrary Allaah ordered them to perform the prayer as in chapter 4, verse 102-103. The companions who were the first to embrace Islam used to perform the prayer secretly and when they were persecuted they were ordered to migrate but they were not allowed to abandon the prayer.
The questioner and others who invite to Islam should clarify to the people that Allaah tests His Slaves so that the truthful will become distinct from the liars. Allaah Says (what means): {Do the people think that they will be left to say: ''We believe'', and they will not be tried? But We have certainly tried those before them, and Allaah will surely make evident those who are truthful, and He will surely make evident the liars.}[Quran 29:2-3]. So the people who invite to Islam should prepare the new Muslims to this effect and remind them to be patient and that the blessed end would be for the pious.
Allaah Knows best.